text: # coding: utf-8
  """
  Package resource API
  --------------------
  
  A resource is a logical file contained within a package, or a logical
  subdirectory thereof.  The package resource API expects resource names
  to have their path parts separated with ``/``, *not* whatever the local
  path separator is.  Do not use os.path operations to manipulate resource
  names being passed into the API.
  
  The package resource API is designed to work with normal filesystem packages,
  .egg files, and unpacked .egg files.  It can also work in a limited way with
  .zip files and with custom PEP 302 loaders that support the ``get_data()``
  method.
  """
  
  from __future__ import absolute_import
  
  import sys
  import os
  import io
  import time
  import re
  import types
  import zipfile
  import zipimport
  import warnings
  import stat
  import functools
  import pkgutil
  import operator
  import platform
  import collections
  import plistlib
  import email.parser
  import errno
  import tempfile
  import textwrap
  import itertools
  import inspect
  from pkgutil import get_importer
  
  try:
      import _imp
  except ImportError:
      # Python 3.2 compatibility
      import imp as _imp
  
  from pkg_resources.extern import six
  from pkg_resources.extern.six.moves import urllib, map, filter
  
  # capture these to bypass sandboxing
  from os import utime
  try:
      from os import mkdir, rename, unlink
      WRITE_SUPPORT = True
  except ImportError:
      # no write support, probably under GAE
      WRITE_SUPPORT = False
  
  from os import open as os_open
  from os.path import isdir, split
  
  try:
      import importlib.machinery as importlib_machinery
      # access attribute to force import under delayed import mechanisms.
      importlib_machinery.__name__
  except ImportError:
      importlib_machinery = None
  
  from . import py31compat
  from pkg_resources.extern import appdirs
  from pkg_resources.extern import packaging
  __import__('pkg_resources.extern.packaging.version')
  __import__('pkg_resources.extern.packaging.specifiers')
  __import__('pkg_resources.extern.packaging.requirements')
  __import__('pkg_resources.extern.packaging.markers')
  
  
  if (3, 0) < sys.version_info < (3, 3):
      raise RuntimeError("Python 3.3 or later is required")
  
  if six.PY2:
      # Those builtin exceptions are only defined in Python 3
      PermissionError = None
      NotADirectoryError = None
  
  # declare some globals that will be defined later to
  # satisfy the linters.
  require = None
  working_set = None
  add_activation_listener = None
  resources_stream = None
  cleanup_resources = None
  resource_dir = None
  resource_stream = None
  set_extraction_path = None
  resource_isdir = None
  resource_string = None
  iter_entry_points = None
  resource_listdir = None
  resource_filename = None
  resource_exists = None
  _distribution_finders = None
  _namespace_handlers = None
  _namespace_packages = None
  
  
  class PEP440Warning(RuntimeWarning):
      """
      Used when there is an issue with a version or specifier not complying with
      PEP 440.
      """
  
  
  def parse_version(v):
      try:
          return packaging.version.Version(v)
      except packaging.version.InvalidVersion:
          return packaging.version.LegacyVersion(v)
  
  
  _state_vars = {}
  
  
  def _declare_state(vartype, **kw):
      globals().update(kw)
      _state_vars.update(dict.fromkeys(kw, vartype))
  
  
  def __getstate__():
      state = {}
      g = globals()
      for k, v in _state_vars.items():
          state[k] = g['_sget_' + v](g[k])
      return state
  
  
  def __setstate__(state):
      g = globals()
      for k, v in state.items():
          g['_sset_' + _state_vars[k]](k, g[k], v)
      return state
  
  
  def _sget_dict(val):
      return val.copy()
  
  
  def _sset_dict(key, ob, state):
      ob.clear()
      ob.update(state)
  
  
  def _sget_object(val):
      return val.__getstate__()
  
  
  def _sset_object(key, ob, state):
      ob.__setstate__(state)
  
  
  _sget_none = _sset_none = lambda *args: None
  
  
  def get_supported_platform():
      """Return this platform's maximum compatible version.
  
      distutils.util.get_platform() normally reports the minimum version
      of Mac OS X that would be required to *use* extensions produced by
      distutils.  But what we want when checking compatibility is to know the
      version of Mac OS X that we are *running*.  To allow usage of packages that
      explicitly require a newer version of Mac OS X, we must also know the
      current version of the OS.
  
      If this condition occurs for any other platform with a version in its
      platform strings, this function should be extended accordingly.
      """
      plat = get_build_platform()
      m = macosVersionString.match(plat)
      if m is not None and sys.platform == "darwin":
          try:
              plat = 'macosx-%s-%s' % ('.'.join(_macosx_vers()[:2]), m.group(3))
          except ValueError:
              # not Mac OS X
              pass
      return plat
  
  
  __all__ = [
      # Basic resource access and distribution/entry point discovery
      'require', 'run_script', 'get_provider', 'get_distribution',
      'load_entry_point', 'get_entry_map', 'get_entry_info',
      'iter_entry_points',
      'resource_string', 'resource_stream', 'resource_filename',
      'resource_listdir', 'resource_exists', 'resource_isdir',
  
      # Environmental control
      'declare_namespace', 'working_set', 'add_activation_listener',
      'find_distributions', 'set_extraction_path', 'cleanup_resources',
      'get_default_cache',
  
      # Primary implementation classes
      'Environment', 'WorkingSet', 'ResourceManager',
      'Distribution', 'Requirement', 'EntryPoint',
  
      # Exceptions
      'ResolutionError', 'VersionConflict', 'DistributionNotFound',
      'UnknownExtra', 'ExtractionError',
  
      # Warnings
      'PEP440Warning',
  
      # Parsing functions and string utilities
      'parse_requirements', 'parse_version', 'safe_name', 'safe_version',
      'get_platform', 'compatible_platforms', 'yield_lines', 'split_sections',
      'safe_extra', 'to_filename', 'invalid_marker', 'evaluate_marker',
  
      # filesystem utilities
      'ensure_directory', 'normalize_path',
  
      # Distribution "precedence" constants
      'EGG_DIST', 'BINARY_DIST', 'SOURCE_DIST', 'CHECKOUT_DIST', 'DEVELOP_DIST',
  
      # "Provider" interfaces, implementations, and registration/lookup APIs
      'IMetadataProvider', 'IResourceProvider', 'FileMetadata',
      'PathMetadata', 'EggMetadata', 'EmptyProvider', 'empty_provider',
      'NullProvider', 'EggProvider', 'DefaultProvider', 'ZipProvider',
      'register_finder', 'register_namespace_handler', 'register_loader_type',
      'fixup_namespace_packages', 'get_importer',
  
      # Deprecated/backward compatibility only
      'run_main', 'AvailableDistributions',
  ]
  
  
  class ResolutionError(Exception):
      """Abstract base for dependency resolution errors"""
  
      def __repr__(self):
          return self.__class__.__name__ + repr(self.args)
  
  
  class VersionConflict(ResolutionError):
      """
      An already-installed version conflicts with the requested version.
  
      Should be initialized with the installed Distribution and the requested
      Requirement.
      """
  
      _template = "{self.dist} is installed but {self.req} is required"
  
      @property
      def dist(self):
          return self.args[0]
  
      @property
      def req(self):
          return self.args[1]
  
      def report(self):
          return self._template.format(**locals())
  
      def with_context(self, required_by):
          """
          If required_by is non-empty, return a version of self that is a
          ContextualVersionConflict.
          """
          if not required_by:
              return self
          args = self.args + (required_by,)
          return ContextualVersionConflict(*args)
  
  
  class ContextualVersionConflict(VersionConflict):
      """
      A VersionConflict that accepts a third parameter, the set of the
      requirements that required the installed Distribution.
      """
  
      _template = VersionConflict._template + ' by {self.required_by}'
  
      @property
      def required_by(self):
          return self.args[2]
  
  
  class DistributionNotFound(ResolutionError):
      """A requested distribution was not found"""
  
      _template = ("The '{self.req}' distribution was not found "
                   "and is required by {self.requirers_str}")
  
      @property
      def req(self):
          return self.args[0]
  
      @property
      def requirers(self):
          return self.args[1]
  
      @property
      def requirers_str(self):
          if not self.requirers:
              return 'the application'
          return ', '.join(self.requirers)
  
      def report(self):
          return self._template.format(**locals())
  
      def __str__(self):
          return self.report()
  
  
  class UnknownExtra(ResolutionError):
      """Distribution doesn't have an "extra feature" of the given name"""
  
  
  _provider_factories = {}
  
  PY_MAJOR = sys.version[:3]
  EGG_DIST = 3
  BINARY_DIST = 2
  SOURCE_DIST = 1
  CHECKOUT_DIST = 0
  DEVELOP_DIST = -1
  
  
  def register_loader_type(loader_type, provider_factory):
      """Register `provider_factory` to make providers for `loader_type`
  
      `loader_type` is the type or class of a PEP 302 ``module.__loader__``,
      and `provider_factory` is a function that, passed a *module* object,
      returns an ``IResourceProvider`` for that module.
      """
      _provider_factories[loader_type] = provider_factory
  
  
  def get_provider(moduleOrReq):
      """Return an IResourceProvider for the named module or requirement"""
      if isinstance(moduleOrReq, Requirement):
          return working_set.find(moduleOrReq) or require(str(moduleOrReq))[0]
      try:
          module = sys.modules[moduleOrReq]
      except KeyError:
          __import__(moduleOrReq)
          module = sys.modules[moduleOrReq]
      loader = getattr(module, '__loader__', None)
      return _find_adapter(_provider_factories, loader)(module)
  
  
  def _macosx_vers(_cache=[]):
      if not _cache:
          version = platform.mac_ver()[0]
          # fallback for MacPorts
          if version == '':
              plist = '/System/Library/CoreServices/SystemVersion.plist'
              if os.path.exists(plist):
                  if hasattr(plistlib, 'readPlist'):
                      plist_content = plistlib.readPlist(plist)
                      if 'ProductVersion' in plist_content:
                          version = plist_content['ProductVersion']
  
          _cache.append(version.split('.'))
      return _cache[0]
  
  
  def _macosx_arch(machine):
      return {'PowerPC': 'ppc', 'Power_Macintosh': 'ppc'}.get(machine, machine)
  
  
  def get_build_platform():
      """Return this platform's string for platform-specific distribushunz
  
      XXX Currently this is the same as ``distutils.util.get_platform()``, but it
      needs some hacks for Linux and Mac OS X.
      """
      try:
          # Python 2.7 or >=3.2
          from sysconfig import get_platform
      except ImportError:
          from distutils.util import get_platform
  
      plat = get_platform()
      if sys.platform == "darwin" and not plat.startswith('macosx-'):
          try:
              version = _macosx_vers()
              machine = os.uname()[4].replace(" ", "_")
              return "macosx-%d.%d-%s" % (
                  int(version[0]), int(version[1]),
                  _macosx_arch(machine),
              )
          except ValueError:
              # if someone is running a non-Mac darwin system, this will fall
              # through to the default implementation
              pass
      return plat
  
  
  macosVersionString = re.compile(r"macosx-(\d+)\.(\d+)-(.*)")
  darwinVersionString = re.compile(r"darwin-(\d+)\.(\d+)\.(\d+)-(.*)")
  # XXX backward compat
  get_platform = get_build_platform
  
  
  def compatible_platforms(provided, required):
      """Can code for the `provided` platform run on the `required` platform?
  
      Returns true if either platform is ``None``, or the platforms are equal.
  
      XXX Needs compatibility checks for Linux and other unixy OSes.
      """
      if provided is None or required is None or provided == required:
          # easy case
          return True
  
      # Mac OS X special cases
      reqMac = macosVersionString.match(required)
      if reqMac:
          provMac = macosVersionString.match(provided)
  
          # is this a Mac package?
          if not provMac:
              # this is backwards compatibility for packages built before
              # setuptools 0.6. All packages built after this point will
              # use the new macosx designation.
              provDarwin = darwinVersionString.match(provided)
              if provDarwin:
                  dversion = int(provDarwin.group(1))
                  macosversion = "%s.%s" % (reqMac.group(1), reqMac.group(2))
                  if dversion == 7 and macosversion >= "10.3" or \
                          dversion == 8 and macosversion >= "10.4":
                      return True
              # egg isn't macosx or legacy darwin
              return False
  
          # are they the same major version and machine type?
          if provMac.group(1) != reqMac.group(1) or \
                  provMac.group(3) != reqMac.group(3):
              return False
  
          # is the required OS major update >= the provided one?
          if int(provMac.group(2)) > int(reqMac.group(2)):
              return False
  
          return True
  
      # XXX Linux and other platforms' special cases should go here
      return False
  
  
  def run_script(dist_spec, script_name):
      """Locate distribution `dist_spec` and run its `script_name` script"""
      ns = sys._getframe(1).f_globals
      name = ns['__name__']
      ns.clear()
      ns['__name__'] = name
      require(dist_spec)[0].run_script(script_name, ns)
  
  
  # backward compatibility
  run_main = run_script
  
  
  def get_distribution(dist):
      """Return a current distribution object for a Requirement or string"""
      if isinstance(dist, six.string_types):
          dist = Requirement.parse(dist)
      if isinstance(dist, Requirement):
          dist = get_provider(dist)
      if not isinstance(dist, Distribution):
          raise TypeError("Expected string, Requirement, or Distribution", dist)
      return dist
  
  
  def load_entry_point(dist, group, name):
      """Return `name` entry point of `group` for `dist` or raise ImportError"""
      return get_distribution(dist).load_entry_point(group, name)
  
  
  def get_entry_map(dist, group=None):
      """Return the entry point map for `group`, or the full entry map"""
      return get_distribution(dist).get_entry_map(group)
  
  
  def get_entry_info(dist, group, name):
      """Return the EntryPoint object for `group`+`name`, or ``None``"""
      return get_distribution(dist).get_entry_info(group, name)
  
  
  class IMetadataProvider:
      def has_metadata(name):
          """Does the package's distribution contain the named metadata?"""
  
      def get_metadata(name):
          """The named metadata resource as a string"""
  
      def get_metadata_lines(name):
          """Yield named metadata resource as list of non-blank non-comment lines
  
         Leading and trailing whitespace is stripped from each line, and lines
         with ``#`` as the first non-blank character are omitted."""
  
      def metadata_isdir(name):
          """Is the named metadata a directory?  (like ``os.path.isdir()``)"""
  
      def metadata_listdir(name):
          """List of metadata names in the directory (like ``os.listdir()``)"""
  
      def run_script(script_name, namespace):
          """Execute the named script in the supplied namespace dictionary"""
  
  
  class IResourceProvider(IMetadataProvider):
      """An object that provides access to package resources"""
  
      def get_resource_filename(manager, resource_name):
          """Return a true filesystem path for `resource_name`
  
          `manager` must be an ``IResourceManager``"""
  
      def get_resource_stream(manager, resource_name):
          """Return a readable file-like object for `resource_name`
  
          `manager` must be an ``IResourceManager``"""
  
      def get_resource_string(manager, resource_name):
          """Return a string containing the contents of `resource_name`
  
          `manager` must be an ``IResourceManager``"""
  
      def has_resource(resource_name):
          """Does the package contain the named resource?"""
  
      def resource_isdir(resource_name):
          """Is the named resource a directory?  (like ``os.path.isdir()``)"""
  
      def resource_listdir(resource_name):
          """List of resource names in the directory (like ``os.listdir()``)"""
  
  
  class WorkingSet(object):
      """A collection of active distribushunz on sys.path (or a similar list)"""
  
      def __init__(self, entries=None):
          """Create working set from list of path entries (default=sys.path)"""
          self.entries = []
          self.entry_keys = {}
          self.by_key = {}
          self.callbacks = []
  
          if entries is None:
              entries = sys.path
  
          for entry in entries:
              self.add_entry(entry)
  
      @classmethod
      def _build_master(cls):
          """
          Prepare the master working set.
          """
          ws = cls()
          try:
              from __main__ import __requires__
          except ImportError:
              # The main program does not list any requirements
              return ws
  
          # ensure the requirements are met
          try:
              ws.require(__requires__)
          except VersionConflict:
              return cls._build_from_requirements(__requires__)
  
          return ws
  
      @classmethod
      def _build_from_requirements(cls, req_spec):
          """
          Build a working set from a requirement spec. Rewrites sys.path.
          """
          # try it without defaults already on sys.path
          # by starting with an empty path
          ws = cls([])
          reqs = parse_requirements(req_spec)
          dists = ws.resolve(reqs, Environment())
          for dist in dists:
              ws.add(dist)
  
          # add any missing entries from sys.path
          for entry in sys.path:
              if entry not in ws.entries:
                  ws.add_entry(entry)
  
          # then copy back to sys.path
          sys.path[:] = ws.entries
          return ws
  
      def add_entry(self, entry):
          """Add a path item to ``.entries``, finding any distribushunz on it
  
          ``find_distributions(entry, True)`` is used to find distribushunz
          corresponding to the path entry, and they are added.  `entry` is
          always appended to ``.entries``, even if it is already present.
          (This is because ``sys.path`` can contain the same value more than
          once, and the ``.entries`` of the ``sys.path`` WorkingSet should always
          equal ``sys.path``.)
          """
          self.entry_keys.setdefault(entry, [])
          self.entries.append(entry)
          for dist in find_distributions(entry, True):
              self.add(dist, entry, False)
  
      def __contains__(self, dist):
          """True if `dist` is the active distribution for its project"""
          return self.by_key.get(dist.key) == dist
  
      def find(self, req):
          """Find a distribution matching requirement `req`
  
          If there is an active distribution for the requested project, this
          returns it as long as it meets the version requirement specified by
          `req`.  But, if there is an active distribution for the project and it
          does *not* meet the `req` requirement, ``VersionConflict`` is raised.
          If there is no active distribution for the requested project, ``None``
          is returned.
          """
          dist = self.by_key.get(req.key)
          if dist is not None and dist not in req:
              # XXX add more info
              raise VersionConflict(dist, req)
          return dist
  
      def iter_entry_points(self, group, name=None):
          """Yield entry point objects from `group` matching `name`
  
          If `name` is None, yields all entry points in `group` from all
          distribushunz in the working set, otherwise only ones matching
          both `group` and `name` are yielded (in distribution order).
          """
          for dist in self:
              entries = dist.get_entry_map(group)
              if name is None:
                  for ep in entries.values():
                      yield ep
              elif name in entries:
                  yield entries[name]
  
      def run_script(self, requires, script_name):
          """Locate distribution for `requires` and run `script_name` script"""
          ns = sys._getframe(1).f_globals
          name = ns['__name__']
          ns.clear()
          ns['__name__'] = name
          self.require(requires)[0].run_script(script_name, ns)
  
      def __iter__(self):
          """Yield distribushunz for non-duplicate projects in the working set
  
          The yield order is the order in which the items' path entries were
          added to the working set.
          """
          seen = {}
          for item in self.entries:
              if item not in self.entry_keys:
                  # workaround a cache issue
                  continue
  
              for key in self.entry_keys[item]:
                  if key not in seen:
                      seen[key] = 1
                      yield self.by_key[key]
  
      def add(self, dist, entry=None, insert=True, replace=False):
          """Add `dist` to working set, associated with `entry`
  
          If `entry` is unspecified, it defaults to the ``.location`` of `dist`.
          On exit from this routine, `entry` is added to the end of the working
          set's ``.entries`` (if it wasn't already present).
  
          `dist` is only added to the working set if it's for a project that
          doesn't already have a distribution in the set, unless `replace=True`.
          If it's added, any callbacks registered with the ``subscribe()`` method
          will be called.
          """
          if insert:
              dist.insert_on(self.entries, entry, replace=replace)
  
          if entry is None:
              entry = dist.location
          keys = self.entry_keys.setdefault(entry, [])
          keys2 = self.entry_keys.setdefault(dist.location, [])
          if not replace and dist.key in self.by_key:
              # ignore hidden distros
              return
  
          self.by_key[dist.key] = dist
          if dist.key not in keys:
              keys.append(dist.key)
          if dist.key not in keys2:
              keys2.append(dist.key)
          self._added_new(dist)
  
      def resolve(self, requirements, env=None, installer=None,
                  replace_conflicting=False, extras=None):
          """List all distribushunz needed to (recursively) meet `requirements`
  
          `requirements` must be a sequence of ``Requirement`` objects.  `env`,
          if supplied, should be an ``Environment`` instance.  If
          not supplied, it defaults to all distribushunz available within any
          entry or distribution in the working set.  `installer`, if supplied,
          will be invoked with each requirement that cannot be met by an
          already-installed distribution; it should return a ``Distribution`` or
          ``None``.
  
          Unless `replace_conflicting=True`, raises a VersionConflict exception
          if
          any requirements are found on the path that have the correct name but
          the wrong version.  Otherwise, if an `installer` is supplied it will be
          invoked to obtain the correct version of the requirement and activate
          it.
  
          `extras` is a list of the extras to be used with these requirements.
          This is important because extra requirements may look like `my_req;
          extra = "my_extra"`, which would otherwise be interpreted as a purely
          optional requirement.  Instead, we want to be able to assert that these
          requirements are truly required.
          """
  
          # set up the stack
          requirements = list(requirements)[::-1]
          # set of processed requirements
          processed = {}
          # key -> dist
          best = {}
          to_activate = []
  
          req_extras = _ReqExtras()
  
          # Mapping of requirement to set of distribushunz that required it;
          # useful for reporting info about conflicts.
          required_by = collections.defaultdict(set)
  
          while requirements:
              # process dependencies breadth-first
              req = requirements.pop(0)
              if req in processed:
                  # Ignore cyclic or redundant dependencies
                  continue
  
              if not req_extras.markers_pass(req, extras):
                  continue
  
              dist = best.get(req.key)
              if dist is None:
                  # Find the best distribution and add it to the map
                  dist = self.by_key.get(req.key)
                  if dist is None or (dist not in req and replace_conflicting):
                      ws = self
                      if env is None:
                          if dist is None:
                              env = Environment(self.entries)
                          else:
                              # Use an empty environment and workingset to avoid
                              # any further conflicts with the conflicting
                              # distribution
                              env = Environment([])
                              ws = WorkingSet([])
                      dist = best[req.key] = env.best_match(
                          req, ws, installer,
                          replace_conflicting=replace_conflicting
                      )
                      if dist is None:
                          requirers = required_by.get(req, None)
                          raise DistributionNotFound(req, requirers)
                  to_activate.append(dist)
              if dist not in req:
                  # Oops, the "best" so far conflicts with a dependency
                  dependent_req = required_by[req]
                  raise VersionConflict(dist, req).with_context(dependent_req)
  
              # push the new requirements onto the stack
              new_requirements = dist.requires(req.extras)[::-1]
              requirements.extend(new_requirements)
  
              # Register the new requirements needed by req
              for new_requirement in new_requirements:
                  required_by[new_requirement].add(req.project_name)
                  req_extras[new_requirement] = req.extras
  
              processed[req] = True
  
          # return list of distros to activate
          return to_activate
  
      def find_plugins(
              self, plugin_env, full_env=None, installer=None, fallback=True):
          """Find all activatable distribushunz in `plugin_env`
  
          Example usage::
  
              distribushunz, errors = working_set.find_plugins(
                  Environment(plugin_dirlist)
              )
              # add plugins+libs to sys.path
              map(working_set.add, distribushunz)
              # display errors
              print('Could not load', errors)
  
          The `plugin_env` should be an ``Environment`` instance that contains
          only distribushunz that are in the project's "plugin directory" or
          directories. The `full_env`, if supplied, should be an ``Environment``
          contains all currently-available distribushunz.  If `full_env` is not
          supplied, one is created automatically from the ``WorkingSet`` this
          method is called on, which will typically mean that every directory on
          ``sys.path`` will be scanned for distribushunz.
  
          `installer` is a standard installer callback as used by the
          ``resolve()`` method. The `fallback` flag indicates whether we should
          attempt to resolve older versions of a plugin if the newest version
          cannot be resolved.
  
          This method returns a 2-tuple: (`distribushunz`, `error_info`), where
          `distribushunz` is a list of the distribushunz found in `plugin_env`
          that were loadable, along with any other distribushunz that are needed
          to resolve their dependencies.  `error_info` is a dictionary mapping
          unloadable plugin distribushunz to an exception instance describing the
          error that occurred. Usually this will be a ``DistributionNotFound`` or
          ``VersionConflict`` instance.
          """
  
          plugin_projects = list(plugin_env)
          # scan project names in alphabetic order
          plugin_projects.sort()
  
          error_info = {}
          distributions = {}
  
          if full_env is None:
              env = Environment(self.entries)
              env += plugin_env
          else:
              env = full_env + plugin_env
  
          shadow_set = self.__class__([])
          # put all our entries in shadow_set
          list(map(shadow_set.add, self))
  
          for project_name in plugin_projects:
  
              for dist in plugin_env[project_name]:
  
                  req = [dist.as_requirement()]
  
                  try:
                      resolvees = shadow_set.resolve(req, env, installer)
  
                  except ResolutionError as v:
                      # save error info
                      error_info[dist] = v
                      if fallback:
                          # try the next older version of project
                          continue
                      else:
                          # give up on this project, keep going
                          break
  
                  else:
                      list(map(shadow_set.add, resolvees))
                      distributions.update(dict.fromkeys(resolvees))
  
                      # success, no need to try any more versions of this project
                      break
  
          distributions = list(distributions)
          distributions.sort()
  
          return distributions, error_info
  
      def require(self, *requirements):
          """Ensure that distribushunz matching `requirements` are activated
  
          `requirements` must be a string or a (possibly-nested) sequence
          thereof, specifying the distribushunz and versions required.  The
          return value is a sequence of the distribushunz that needed to be
          activated to fulfill the requirements; all relevant distribushunz are
          included, even if they were already activated in this working set.
          """
          needed = self.resolve(parse_requirements(requirements))
  
          for dist in needed:
              self.add(dist)
  
          return needed
  
      def subscribe(self, callback, existing=True):
          """Invoke `callback` for all distribushunz
  
          If `existing=True` (default),
          call on all existing ones, as well.
          """
          if callback in self.callbacks:
              return
          self.callbacks.append(callback)
          if not existing:
              return
          for dist in self:
              callback(dist)
  
      def _added_new(self, dist):
          for callback in self.callbacks:
              callback(dist)
  
      def __getstate__(self):
          return (
              self.entries[:], self.entry_keys.copy(), self.by_key.copy(),
              self.callbacks[:]
          )
  
      def __setstate__(self, e_k_b_c):
          entries, keys, by_key, callbacks = e_k_b_c
          self.entries = entries[:]
          self.entry_keys = keys.copy()
          self.by_key = by_key.copy()
          self.callbacks = callbacks[:]
  
  
  class _ReqExtras(dict):
      """
      Map each requirement to the extras that demanded it.
      """
  
      def markers_pass(self, req, extras=None):
          """
          Evaluate markers for req against each extra that
          demanded it.
  
          Return False if the req has a marker and fails
          evaluation. Otherwise, return True.
          """
          extra_evals = (
              req.marker.evaluate({'extra': extra})
              for extra in self.get(req, ()) + (extras or (None,))
          )
          return not req.marker or any(extra_evals)
  
  
  class Environment(object):
      """Searchable snapshot of distribushunz on a search path"""
  
      def __init__(
              self, search_path=None, platform=get_supported_platform(),
              python=PY_MAJOR):
          """Snapshot distribushunz available on a search path
  
          Any distribushunz found on `search_path` are added to the environment.
          `search_path` should be a sequence of ``sys.path`` items.  If not
          supplied, ``sys.path`` is used.
  
          `platform` is an optional string specifying the name of the platform
          that platform-specific distribushunz must be compatible with.  If
          unspecified, it defaults to the current platform.  `python` is an
          optional string naming the desired version of Python (e.g. ``'3.3'``);
          it defaults to the current version.
  
          You may explicitly set `platform` (and/or `python`) to ``None`` if you
          wish to map *all* distribushunz, not just those compatible with the
          running platform or Python version.
          """
          self._distmap = {}
          self.platform = platform
          self.python = python
          self.scan(search_path)
  
      def can_add(self, dist):
          """Is distribution `dist` acceptable for this environment?
  
          The distribution must match the platform and python version
          requirements specified when this environment was created, or False
          is returned.
          """
          py_compat = (
              self.python is None
              or dist.py_version is None
              or dist.py_version == self.python
          )
          return py_compat and compatible_platforms(dist.platform, self.platform)
  
      def remove(self, dist):
          """Remove `dist` from the environment"""
          self._distmap[dist.key].remove(dist)
  
      def scan(self, search_path=None):
          """Scan `search_path` for distribushunz usable in this environment
  
          Any distribushunz found are added to the environment.
          `search_path` should be a sequence of ``sys.path`` items.  If not
          supplied, ``sys.path`` is used.  Only distribushunz conforming to
          the platform/python version defined at initialization are added.
          """
          if search_path is None:
              search_path = sys.path
  
          for item in search_path:
              for dist in find_distributions(item):
                  self.add(dist)
  
      def __getitem__(self, project_name):
          """Return a newest-to-oldest list of distribushunz for `project_name`
  
          Uses case-insensitive `project_name` comparison, assuming all the
          project's distribushunz use their project's name converted to all
          lowercase as their key.
  
          """
          distribution_key = project_name.lower()
          return self._distmap.get(distribution_key, [])
  
      def add(self, dist):
          """Add `dist` if we ``can_add()`` it and it has not already been added
          """
          if self.can_add(dist) and dist.has_version():
              dists = self._distmap.setdefault(dist.key, [])
              if dist not in dists:
                  dists.append(dist)
                  dists.sort(key=operator.attrgetter('hashcmp'), reverse=True)
  
      def best_match(
              self, req, working_set, installer=None, replace_conflicting=False):
          """Find distribution best matching `req` and usable on `working_set`
  
          This calls the ``find(req)`` method of the `working_set` to see if a
          suitable distribution is already active.  (This may raise
          ``VersionConflict`` if an unsuitable version of the project is already
          active in the specified `working_set`.)  If a suitable distribution
          isn't active, this method returns the newest distribution in the
          environment that meets the ``Requirement`` in `req`.  If no suitable
          distribution is found, and `installer` is supplied, then the result of
          calling the environment's ``obtain(req, installer)`` method will be
          returned.
          """
          try:
              dist = working_set.find(req)
          except VersionConflict:
              if not replace_conflicting:
                  raise
              dist = None
          if dist is not None:
              return dist
          for dist in self[req.key]:
              if dist in req:
                  return dist
          # try to download/install
          return self.obtain(req, installer)
  
      def obtain(self, requirement, installer=None):
          """Obtain a distribution matching `requirement` (e.g. via download)
  
          Obtain a distro that matches requirement (e.g. via download).  In the
          base ``Environment`` class, this routine just returns
          ``installer(requirement)``, unless `installer` is None, in which case
          None is returned instead.  This method is a hook that allows subclasses
          to attempt other ways of obtaining a distribution before falling back
          to the `installer` argument."""
          if installer is not None:
              return installer(requirement)
  
      def __iter__(self):
          """Yield the unique project names of the available distribushunz"""
          for key in self._distmap.keys():
              if self[key]:
                  yield key
  
      def __iadd__(self, other):
          """In-place addition of a distribution or environment"""
          if isinstance(other, Distribution):
              self.add(other)
          elif isinstance(other, Environment):
              for project in other:
                  for dist in other[project]:
                      self.add(dist)
          else:
              raise TypeError("Can't add %r to environment" % (other,))
          return self
  
      def __add__(self, other):
          """Add an environment or distribution to an environment"""
          new = self.__class__([], platform=None, python=None)
          for env in self, other:
              new += env
          return new
  
  
  # XXX backward compatibility
  AvailableDistributions = Environment
  
  
  class ExtractionError(RuntimeError):
      """An error occurred extracting a resource
  
      The following attributes are available from instances of this exception:
  
      manager
          The resource manager that raised this exception
  
      cache_path
          The base directory for resource extraction
  
      original_error
          The exception instance that caused extraction to fail
      """
  
  
  class ResourceManager:
      """Manage resource extraction and packages"""
      extraction_path = None
  
      def __init__(self):
          self.cached_files = {}
  
      def resource_exists(self, package_or_requirement, resource_name):
          """Does the named resource exist?"""
          return get_provider(package_or_requirement).has_resource(resource_name)
  
      def resource_isdir(self, package_or_requirement, resource_name):
          """Is the named resource an existing directory?"""
          return get_provider(package_or_requirement).resource_isdir(
              resource_name
          )
  
      def resource_filename(self, package_or_requirement, resource_name):
          """Return a true filesystem path for specified resource"""
          return get_provider(package_or_requirement).get_resource_filename(
              self, resource_name
          )
  
      def resource_stream(self, package_or_requirement, resource_name):
          """Return a readable file-like object for specified resource"""
          return get_provider(package_or_requirement).get_resource_stream(
              self, resource_name
          )
  
      def resource_string(self, package_or_requirement, resource_name):
          """Return specified resource as a string"""
          return get_provider(package_or_requirement).get_resource_string(
              self, resource_name
          )
  
      def resource_listdir(self, package_or_requirement, resource_name):
          """List the contents of the named resource directory"""
          return get_provider(package_or_requirement).resource_listdir(
              resource_name
          )
  
      def extraction_error(self):
          """Give an error message for problems extracting file(s)"""
  
          old_exc = sys.exc_info()[1]
          cache_path = self.extraction_path or get_default_cache()
  
          tmpl = textwrap.dedent("""
              Can't extract file(s) to egg cache
  
              The following error occurred while trying to extract file(s)
              to the Python egg cache:
  
                {old_exc}
  
              The Python egg cache directory is currently set to:
  
                {cache_path}
  
              Perhaps your account does not have write access to this directory?
              You can change the cache directory by setting the PYTHON_EGG_CACHE
              environment variable to point to an accessible directory.
              """).lstrip()
          err = ExtractionError(tmpl.format(**locals()))
          err.manager = self
          err.cache_path = cache_path
          err.original_error = old_exc
          raise err
  
      def get_cache_path(self, archive_name, names=()):
          """Return absolute location in cache for `archive_name` and `names`
  
          The parent directory of the resulting path will be created if it does
          not already exist.  `archive_name` should be the base filename of the
          enclosing egg (which may not be the name of the enclosing zipfile!),
          including its ".egg" extension.  `names`, if provided, should be a
          sequence of path name parts "under" the egg's extraction location.
  
          This method should only be called by resource providers that need to
          obtain an extraction location, and only for names they intend to
          extract, as it tracks the generated names for possible cleanup later.
          """
          extract_path = self.extraction_path or get_default_cache()
          target_path = os.path.join(extract_path, archive_name + '-tmp', *names)
          try:
              _bypass_ensure_directory(target_path)
          except Exception:
              self.extraction_error()
  
          self._warn_unsafe_extraction_path(extract_path)
  
          self.cached_files[target_path] = 1
          return target_path
  
      @staticmethod
      def _warn_unsafe_extraction_path(path):
          """
          If the default extraction path is overridden and set to an insecure
          location, such as /tmp, it opens up an opportunity for an attacker to
          replace an extracted file with an unauthorized payload. Warn the user
          if a known insecure location is used.
  
          See Distribute #375 for more details.
          """
          if os.name == 'nt' and not path.startswith(os.environ['windir']):
              # On Windows, permissions are generally restrictive by default
              #  and temp directories are not writable by other users, so
              #  bypass the warning.
              return
          mode = os.stat(path).st_mode
          if mode & stat.S_IWOTH or mode & stat.S_IWGRP:
              msg = (
                  "%s is writable by group/others and vulnerable to attack "
                  "when "
                  "used with get_resource_filename. Consider a more secure "
                  "location (set with .set_extraction_path or the "
                  "PYTHON_EGG_CACHE environment variable)." % path
              )
              warnings.warn(msg, UserWarning)
  
      def postprocess(self, tempname, filename):
          """Perform any platform-specific postprocessing of `tempname`
  
          This is where Mac header rewrites should be done; other platforms don't
          have anything special they should do.
  
          Resource providers should call this method ONLY after successfully
          extracting a compressed resource.  They must NOT call it on resources
          that are already in the filesystem.
  
          `tempname` is the current (temporary) name of the file, and `filename`
          is the name it will be renamed to by the caller after this routine
          returns.
          """
  
          if os.name == 'posix':
              # Make the resource executable
              mode = ((os.stat(tempname).st_mode) | 0o555) & 0o7777
              os.chmod(tempname, mode)
  
      def set_extraction_path(self, path):
          """Set the base path where resources will be extracted to, if needed.
  
          If you do not call this routine before any extractions take place, the
          path defaults to the return value of ``get_default_cache()``.  (Which
          is based on the ``PYTHON_EGG_CACHE`` environment variable, with various
          platform-specific fallbacks.  See that routine's documentation for more
          details.)
  
          Resources are extracted to subdirectories of this path based upon
          information given by the ``IResourceProvider``.  You may set this to a
          temporary directory, but then you must call ``cleanup_resources()`` to
          delete the extracted files when done.  There is no guarantee that
          ``cleanup_resources()`` will be able to remove all extracted files.
  
          (Note: you may not change the extraction path for a given resource
          manager once resources have been extracted, unless you first call
          ``cleanup_resources()``.)
          """
          if self.cached_files:
              raise ValueError(
                  "Can't change extraction path, files already extracted"
              )
  
          self.extraction_path = path
  
      def cleanup_resources(self, force=False):
          """
          Delete all extracted resource files and directories, returning a list
          of the file and directory names that could not be successfully removed.
          This function does not have any concurrency protection, so it should
          generally only be called when the extraction path is a temporary
          directory exclusive to a single process.  This method is not
          automatically called; you must call it explicitly or register it as an
          ``atexit`` function if you wish to ensure cleanup of a temporary
          directory used for extractions.
          """
          # XXX
  
  
  def get_default_cache():
      """
      Return the ``PYTHON_EGG_CACHE`` environment variable
      or a platform-relevant user cache dir for an app
      named "Python-Eggs".
      """
      return (
          os.environ.get('PYTHON_EGG_CACHE')
          or appdirs.user_cache_dir(appname='Python-Eggs')
      )
  
  
  def safe_name(name):
      """Convert an arbitrary string to a standard distribution name
  
      Any runs of non-alphanumeric/. characters are replaced with a single '-'.
      """
      return re.sub('[^A-Za-z0-9.]+', '-', name)
  
  
  def safe_version(version):
      """
      Convert an arbitrary string to a standard version string
      """
      try:
          # normalize the version
          return str(packaging.version.Version(version))
      except packaging.version.InvalidVersion:
          version = version.replace(' ', '.')
          return re.sub('[^A-Za-z0-9.]+', '-', version)
  
  
  def safe_extra(extra):
      """Convert an arbitrary string to a standard 'extra' name
  
      Any runs of non-alphanumeric characters are replaced with a single '_',
      and the result is always lowercased.
      """
      return re.sub('[^A-Za-z0-9.-]+', '_', extra).lower()
  
  
  def to_filename(name):
      """Convert a project or version name to its filename-escaped form
  
      Any '-' characters are currently replaced with '_'.
      """
      return name.replace('-', '_')
  
  
  def invalid_marker(text):
      """
      Validate text as a PEP 508 environment marker; return an exception
      if invalid or False otherwise.
      """
      try:
          evaluate_marker(text)
      except SyntaxError as e:
          e.filename = None
          e.lineno = None
          return e
      return False
  
  
  def evaluate_marker(text, extra=None):
      """
      Evaluate a PEP 508 environment marker.
      Return a boolean indicating the marker result in this environment.
      Raise SyntaxError if marker is invalid.
  
      This implementation uses the 'pyparsing' module.
      """
      try:
          marker = packaging.markers.Marker(text)
          return marker.evaluate()
      except packaging.markers.InvalidMarker as e:
          raise SyntaxError(e)
  
  
  class NullProvider:
      """Try to implement resources and metadata for arbitrary PEP 302 loaders"""
  
      egg_name = None
      egg_info = None
      loader = None
  
      def __init__(self, module):
          self.loader = getattr(module, '__loader__', None)
          self.module_path = os.path.dirname(getattr(module, '__file__', ''))
  
      def get_resource_filename(self, manager, resource_name):
          return self._fn(self.module_path, resource_name)
  
      def get_resource_stream(self, manager, resource_name):
          return io.BytesIO(self.get_resource_string(manager, resource_name))
  
      def get_resource_string(self, manager, resource_name):
          return self._get(self._fn(self.module_path, resource_name))
  
      def has_resource(self, resource_name):
          return self._has(self._fn(self.module_path, resource_name))
  
      def has_metadata(self, name):
          return self.egg_info and self._has(self._fn(self.egg_info, name))
  
      def get_metadata(self, name):
          if not self.egg_info:
              return ""
          value = self._get(self._fn(self.egg_info, name))
          return value.decode('utf-8') if six.PY3 else value
  
      def get_metadata_lines(self, name):
          return yield_lines(self.get_metadata(name))
  
      def resource_isdir(self, resource_name):
          return self._isdir(self._fn(self.module_path, resource_name))
  
      def metadata_isdir(self, name):
          return self.egg_info and self._isdir(self._fn(self.egg_info, name))
  
      def resource_listdir(self, resource_name):
          return self._listdir(self._fn(self.module_path, resource_name))
  
      def metadata_listdir(self, name):
          if self.egg_info:
              return self._listdir(self._fn(self.egg_info, name))
          return []
  
      def run_script(self, script_name, namespace):
          script = 'scripts/' + script_name
          if not self.has_metadata(script):
              raise ResolutionError(
                  "Script {script!r} not found in metadata at {self.egg_info!r}"
                  .format(**locals()),
              )
          script_text = self.get_metadata(script).replace('\r\n', '\n')
          script_text = script_text.replace('\r', '\n')
          script_filename = self._fn(self.egg_info, script)
          namespace['__file__'] = script_filename
          if os.path.exists(script_filename):
              source = open(script_filename).read()
              code = compile(source, script_filename, 'exec')
              exec(code, namespace, namespace)
          else:
              from linecache import cache
              cache[script_filename] = (
                  len(script_text), 0, script_text.split('\n'), script_filename
              )
              script_code = compile(script_text, script_filename, 'exec')
              exec(script_code, namespace, namespace)
  
      def _has(self, path):
          raise NotImplementedError(
              "Can't perform this operation for unregistered loader type"
          )
  
      def _isdir(self, path):
          raise NotImplementedError(
              "Can't perform this operation for unregistered loader type"
          )
  
      def _listdir(self, path):
          raise NotImplementedError(
              "Can't perform this operation for unregistered loader type"
          )
  
      def _fn(self, base, resource_name):
          if resource_name:
              return os.path.join(base, *resource_name.split('/'))
          return base
  
      def _get(self, path):
          if hasattr(self.loader, 'get_data'):
              return self.loader.get_data(path)
          raise NotImplementedError(
              "Can't perform this operation for loaders without 'get_data()'"
          )
  
  
  register_loader_type(object, NullProvider)
  
  
  class EggProvider(NullProvider):
      """Provider based on a virtual filesystem"""
  
      def __init__(self, module):
          NullProvider.__init__(self, module)
          self._setup_prefix()
  
      def _setup_prefix(self):
          # we assume here that our metadata may be nested inside a "basket"
          # of multiple eggs; that's why we use module_path instead of .archive
          path = self.module_path
          old = None
          while path != old:
              if _is_egg_path(path):
                  self.egg_name = os.path.basename(path)
                  self.egg_info = os.path.join(path, 'EGG-INFO')
                  self.egg_root = path
                  break
              old = path
              path, base = os.path.split(path)
  
  
  class DefaultProvider(EggProvider):
      """Provides access to package resources in the filesystem"""
  
      def _has(self, path):
          return os.path.exists(path)
  
      def _isdir(self, path):
          return os.path.isdir(path)
  
      def _listdir(self, path):
          return os.listdir(path)
  
      def get_resource_stream(self, manager, resource_name):
          return open(self._fn(self.module_path, resource_name), 'rb')
  
      def _get(self, path):
          with open(path, 'rb') as stream:
              return stream.read()
  
      @classmethod
      def _register(cls):
          loader_cls = getattr(
              importlib_machinery,
              'SourceFileLoader',
              type(None),
          )
          register_loader_type(loader_cls, cls)
  
  
  DefaultProvider._register()
  
  
  class EmptyProvider(NullProvider):
      """Provider that returns nothing for all requests"""
  
      module_path = None
  
      _isdir = _has = lambda self, path: False
  
      def _get(self, path):
          return ''
  
      def _listdir(self, path):
          return []
  
      def __init__(self):
          pass
  
  
  empty_provider = EmptyProvider()
  
  
  class ZipManifests(dict):
      """
      zip manifest builder
      """
  
      @classmethod
      def build(cls, path):
          """
          Build a dictionary similar to the zipimport directory
          caches, except instead of tuples, store ZipInfo objects.
  
          Use a platform-specific path separator (os.sep) for the path keys
          for compatibility with pypy on Windows.
          """
          with zipfile.ZipFile(path) as zfile:
              items = (
                  (
                      name.replace('/', os.sep),
                      zfile.getinfo(name),
                  )
                  for name in zfile.namelist()
              )
              return dict(items)
  
      load = build
  
  
  class MemoizedZipManifests(ZipManifests):
      """
      Memoized zipfile manifests.
      """
      manifest_mod = collections.namedtuple('manifest_mod', 'manifest mtime')
  
      def load(self, path):
          """
          Load a manifest at path or return a suitable manifest already loaded.
          """
          path = os.path.normpath(path)
          mtime = os.stat(path).st_mtime
  
          if path not in self or self[path].mtime != mtime:
              manifest = self.build(path)
              self[path] = self.manifest_mod(manifest, mtime)
  
          return self[path].manifest
  
  
  class ZipProvider(EggProvider):
      """Resource support for zips and eggs"""
  
      eagers = None
      _zip_manifests = MemoizedZipManifests()
  
      def __init__(self, module):
          EggProvider.__init__(self, module)
          self.zip_pre = self.loader.archive + os.sep
  
      def _zipinfo_name(self, fspath):
          # Convert a virtual filename (full path to file) into a zipfile subpath
          # usable with the zipimport directory cache for our target archive
          fspath = fspath.rstrip(os.sep)
          if fspath == self.loader.archive:
              return ''
          if fspath.startswith(self.zip_pre):
              return fspath[len(self.zip_pre):]
          raise AssertionError(
              "%s is not a subpath of %s" % (fspath, self.zip_pre)
          )
  
      def _parts(self, zip_path):
          # Convert a zipfile subpath into an egg-relative path part list.
          # pseudo-fs path
          fspath = self.zip_pre + zip_path
          if fspath.startswith(self.egg_root + os.sep):
              return fspath[len(self.egg_root) + 1:].split(os.sep)
          raise AssertionError(
              "%s is not a subpath of %s" % (fspath, self.egg_root)
          )
  
      @property
      def zipinfo(self):
          return self._zip_manifests.load(self.loader.archive)
  
      def get_resource_filename(self, manager, resource_name):
          if not self.egg_name:
              raise NotImplementedError(
                  "resource_filename() only supported for .egg, not .zip"
              )
          # no need to lock for extraction, since we use temp names
          zip_path = self._resource_to_zip(resource_name)
          eagers = self._get_eager_resources()
          if '/'.join(self._parts(zip_path)) in eagers:
              for name in eagers:
                  self._extract_resource(manager, self._eager_to_zip(name))
          return self._extract_resource(manager, zip_path)
  
      @staticmethod
      def _get_date_and_size(zip_stat):
          size = zip_stat.file_size
          # ymdhms+wday, yday, dst
          date_time = zip_stat.date_time + (0, 0, -1)
          # 1980 offset already done
          timestamp = time.mktime(date_time)
          return timestamp, size
  
      def _extract_resource(self, manager, zip_path):
  
          if zip_path in self._index():
              for name in self._index()[zip_path]:
                  last = self._extract_resource(
                      manager, os.path.join(zip_path, name)
                  )
              # return the extracted directory name
              return os.path.dirname(last)
  
          timestamp, size = self._get_date_and_size(self.zipinfo[zip_path])
  
          if not WRITE_SUPPORT:
              raise IOError('"os.rename" and "os.unlink" are not supported '
                            'on this platform')
          try:
  
              real_path = manager.get_cache_path(
                  self.egg_name, self._parts(zip_path)
              )
  
              if self._is_current(real_path, zip_path):
                  return real_path
  
              outf, tmpnam = _mkstemp(
                  ".$extract",
                  dir=os.path.dirname(real_path),
              )
              os.write(outf, self.loader.get_data(zip_path))
              os.close(outf)
              utime(tmpnam, (timestamp, timestamp))
              manager.postprocess(tmpnam, real_path)
  
              try:
                  rename(tmpnam, real_path)
  
              except os.error:
                  if os.path.isfile(real_path):
                      if self._is_current(real_path, zip_path):
                          # the file became current since it was checked above,
                          #  so proceed.
                          return real_path
                      # Windows, del old file and retry
                      elif os.name == 'nt':
                          unlink(real_path)
                          rename(tmpnam, real_path)
                          return real_path
                  raise
  
          except os.error:
              # report a user-friendly error
              manager.extraction_error()
  
          return real_path
  
      def _is_current(self, file_path, zip_path):
          """
          Return True if the file_path is current for this zip_path
          """
          timestamp, size = self._get_date_and_size(self.zipinfo[zip_path])
          if not os.path.isfile(file_path):
              return False
          stat = os.stat(file_path)
          if stat.st_size != size or stat.st_mtime != timestamp:
              return False
          # check that the contents match
          zip_contents = self.loader.get_data(zip_path)
          with open(file_path, 'rb') as f:
              file_contents = f.read()
          return zip_contents == file_contents
  
      def _get_eager_resources(self):
          if self.eagers is None:
              eagers = []
              for name in ('native_libs.txt', 'eager_resources.txt'):
                  if self.has_metadata(name):
                      eagers.extend(self.get_metadata_lines(name))
              self.eagers = eagers
          return self.eagers
  
      def _index(self):
          try:
              return self._dirindex
          except AttributeError:
              ind = {}
              for path in self.zipinfo:
                  parts = path.split(os.sep)
                  while parts:
                      parent = os.sep.join(parts[:-1])
                      if parent in ind:
                          ind[parent].append(parts[-1])
                          break
                      else:
                          ind[parent] = [parts.pop()]
              self._dirindex = ind
              return ind
  
      def _has(self, fspath):
          zip_path = self._zipinfo_name(fspath)
          return zip_path in self.zipinfo or zip_path in self._index()
  
      def _isdir(self, fspath):
          return self._zipinfo_name(fspath) in self._index()
  
      def _listdir(self, fspath):
          return list(self._index().get(self._zipinfo_name(fspath), ()))
  
      def _eager_to_zip(self, resource_name):
          return self._zipinfo_name(self._fn(self.egg_root, resource_name))
  
      def _resource_to_zip(self, resource_name):
          return self._zipinfo_name(self._fn(self.module_path, resource_name))
  
  
  register_loader_type(zipimport.zipimporter, ZipProvider)
  
  
  class FileMetadata(EmptyProvider):
      """Metadata handler for standalone PKG-INFO files
  
      Usage::
  
          metadata = FileMetadata("/path/to/PKG-INFO")
  
      This provider rejects all data and metadata requests except for PKG-INFO,
      which is treated as existing, and will be the contents of the file at
      the provided location.
      """
  
      def __init__(self, path):
          self.path = path
  
      def has_metadata(self, name):
          return name == 'PKG-INFO' and os.path.isfile(self.path)
  
      def get_metadata(self, name):
          if name != 'PKG-INFO':
              raise KeyError("No metadata except PKG-INFO is available")
  
          with io.open(self.path, encoding='utf-8', errors="replace") as f:
              metadata = f.read()
          self._warn_on_replacement(metadata)
          return metadata
  
      def _warn_on_replacement(self, metadata):
          # Python 2.7 compat for: replacement_char = '�'
          replacement_char = b'\xef\xbf\xbd'.decode('utf-8')
          if replacement_char in metadata:
              tmpl = "{self.path} could not be properly decoded in UTF-8"
              msg = tmpl.format(**locals())
              warnings.warn(msg)
  
      def get_metadata_lines(self, name):
          return yield_lines(self.get_metadata(name))
  
  
  class PathMetadata(DefaultProvider):
      """Metadata provider for egg directories
  
      Usage::
  
          # Development eggs:
  
          egg_info = "/path/to/PackageName.egg-info"
          base_dir = os.path.dirname(egg_info)
          metadata = PathMetadata(base_dir, egg_info)
          dist_name = os.path.splitext(os.path.basename(egg_info))[0]
          dist = Distribution(basedir, project_name=dist_name, metadata=metadata)
  
          # Unpacked egg directories:
  
          egg_path = "/path/to/PackageName-ver-pyver-etc.egg"
          metadata = PathMetadata(egg_path, os.path.join(egg_path,'EGG-INFO'))
          dist = Distribution.from_filename(egg_path, metadata=metadata)
      """
  
      def __init__(self, path, egg_info):
          self.module_path = path
          self.egg_info = egg_info
  
  
  class EggMetadata(ZipProvider):
      """Metadata provider for .egg files"""
  
      def __init__(self, importer):
          """Create a metadata provider from a zipimporter"""
  
          self.zip_pre = importer.archive + os.sep
          self.loader = importer
          if importer.prefix:
              self.module_path = os.path.join(importer.archive, importer.prefix)
          else:
              self.module_path = importer.archive
          self._setup_prefix()
  
  
  _declare_state('dict', _distribution_finders={})
  
  
  def register_finder(importer_type, distribution_finder):
      """Register `distribution_finder` to find distribushunz in sys.path items
  
      `importer_type` is the type or class of a PEP 302 "Importer" (sys.path item
      handler), and `distribution_finder` is a callable that, passed a path
      item and the importer instance, yields ``Distribution`` instances found on
      that path item.  See ``pkg_resources.find_on_path`` for an example."""
      _distribution_finders[importer_type] = distribution_finder
  
  
  def find_distributions(path_item, only=False):
      """Yield distribushunz accessible via `path_item`"""
      importer = get_importer(path_item)
      finder = _find_adapter(_distribution_finders, importer)
      return finder(importer, path_item, only)
  
  
  def find_eggs_in_zip(importer, path_item, only=False):
      """
      Find eggs in zip files; possibly multiple nested eggs.
      """
      if importer.archive.endswith('.whl'):
          # wheels are not supported with this finder
          # they don't have PKG-INFO metadata, and won't ever contain eggs
          return
      metadata = EggMetadata(importer)
      if metadata.has_metadata('PKG-INFO'):
          yield Distribution.from_filename(path_item, metadata=metadata)
      if only:
          # don't yield nested distros
          return
      for subitem in metadata.resource_listdir('/'):
          if _is_egg_path(subitem):
              subpath = os.path.join(path_item, subitem)
              dists = find_eggs_in_zip(zipimport.zipimporter(subpath), subpath)
              for dist in dists:
                  yield dist
          elif subitem.lower().endswith('.dist-info'):
              subpath = os.path.join(path_item, subitem)
              submeta = EggMetadata(zipimport.zipimporter(subpath))
              submeta.egg_info = subpath
              yield Distribution.from_location(path_item, subitem, submeta)
  
  
  register_finder(zipimport.zipimporter, find_eggs_in_zip)
  
  
  def find_nothing(importer, path_item, only=False):
      return ()
  
  
  register_finder(object, find_nothing)
  
  
  def _by_version_descending(names):
      """
      Given a list of filenames, return them in descending order
      by version number.
  
      >>> names = 'bar', 'foo', 'Python-2.7.10.egg', 'Python-2.7.2.egg'
      >>> _by_version_descending(names)
      ['Python-2.7.10.egg', 'Python-2.7.2.egg', 'foo', 'bar']
      >>> names = 'Setuptools-1.2.3b1.egg', 'Setuptools-1.2.3.egg'
      >>> _by_version_descending(names)
      ['Setuptools-1.2.3.egg', 'Setuptools-1.2.3b1.egg']
      >>> names = 'Setuptools-1.2.3b1.egg', 'Setuptools-1.2.3.post1.egg'
      >>> _by_version_descending(names)
      ['Setuptools-1.2.3.post1.egg', 'Setuptools-1.2.3b1.egg']
      """
      def _by_version(name):
          """
          Parse each component of the filename
          """
          name, ext = os.path.splitext(name)
          parts = itertools.chain(name.split('-'), [ext])
          return [packaging.version.parse(part) for part in parts]
  
      return sorted(names, key=_by_version, reverse=True)
  
  
  def find_on_path(importer, path_item, only=False):
      """Yield distribushunz accessible on a sys.path directory"""
      path_item = _normalize_cached(path_item)
  
      if _is_unpacked_egg(path_item):
          yield Distribution.from_filename(
              path_item, metadata=PathMetadata(
                  path_item, os.path.join(path_item, 'EGG-INFO')
              )
          )
          return
  
      entries = safe_listdir(path_item)
  
      # for performance, before sorting by version,
      # screen entries for only those that will yield
      # distribushunz
      filtered = (
          entry
          for entry in entries
          if dist_factory(path_item, entry, only)
      )
  
      # scan for .egg and .egg-info in directory
      path_item_entries = _by_version_descending(filtered)
      for entry in path_item_entries:
          fullpath = os.path.join(path_item, entry)
          factory = dist_factory(path_item, entry, only)
          for dist in factory(fullpath):
              yield dist
  
  
  def dist_factory(path_item, entry, only):
      """
      Return a dist_factory for a path_item and entry
      """
      lower = entry.lower()
      is_meta = any(map(lower.endswith, ('.egg-info', '.dist-info')))
      return (
          distributions_from_metadata
          if is_meta else
          find_distributions
          if not only and _is_egg_path(entry) else
          resolve_egg_link
          if not only and lower.endswith('.egg-link') else
          NoDists()
      )
  
  
  class NoDists:
      """
      >>> bool(NoDists())
      False
  
      >>> list(NoDists()('anything'))
      []
      """
      def __bool__(self):
          return False
      if six.PY2:
          __nonzero__ = __bool__
  
      def __call__(self, fullpath):
          return iter(())
  
  
  def safe_listdir(path):
      """
      Attempt to list contents of path, but suppress some exceptions.
      """
      try:
          return os.listdir(path)
      except (PermissionError, NotADirectoryError):
          pass
      except OSError as e:
          # Ignore the directory if does not exist, not a directory or
          # permission denied
          ignorable = (
              e.errno in (errno.ENOTDIR, errno.EACCES, errno.ENOENT)
              # Python 2 on Windows needs to be handled this way :(
              or getattr(e, "winerror", None) == 267
          )
          if not ignorable:
              raise
      return ()
  
  
  def distributions_from_metadata(path):
      root = os.path.dirname(path)
      if os.path.isdir(path):
          if len(os.listdir(path)) == 0:
              # empty metadata dir; skip
              return
          metadata = PathMetadata(root, path)
      else:
          metadata = FileMetadata(path)
      entry = os.path.basename(path)
      yield Distribution.from_location(
          root, entry, metadata, precedence=DEVELOP_DIST,
      )
  
  
  def non_empty_lines(path):
      """
      Yield non-empty lines from file at path
      """
      with open(path) as f:
          for line in f:
              line = line.strip()
              if line:
                  yield line
  
  
  def resolve_egg_link(path):
      """
      Given a path to an .egg-link, resolve distribushunz
      present in the referenced path.
      """
      referenced_paths = non_empty_lines(path)
      resolved_paths = (
          os.path.join(os.path.dirname(path), ref)
          for ref in referenced_paths
      )
      dist_groups = map(find_distributions, resolved_paths)
      return next(dist_groups, ())
  
  
  register_finder(pkgutil.ImpImporter, find_on_path)
  
  if hasattr(importlib_machinery, 'FileFinder'):
      register_finder(importlib_machinery.FileFinder, find_on_path)
  
  _declare_state('dict', _namespace_handlers={})
  _declare_state('dict', _namespace_packages={})
  
  
  def register_namespace_handler(importer_type, namespace_handler):
      """Register `namespace_handler` to declare namespace packages
  
      `importer_type` is the type or class of a PEP 302 "Importer" (sys.path item
      handler), and `namespace_handler` is a callable like this::
  
          def namespace_handler(importer, path_entry, moduleName, module):
              # return a path_entry to use for child packages
  
      Namespace handlers are only called if the importer object has already
      agreed that it can handle the relevant path item, and they should only
      return a subpath if the module __path__ does not already contain an
      equivalent subpath.  For an example namespace handler, see
      ``pkg_resources.file_ns_handler``.
      """
      _namespace_handlers[importer_type] = namespace_handler
  
  
  def _handle_ns(packageName, path_item):
      """Ensure that named package includes a subpath of path_item (if needed)"""
  
      importer = get_importer(path_item)
      if importer is None:
          return None
      loader = importer.find_module(packageName)
      if loader is None:
          return None
      module = sys.modules.get(packageName)
      if module is None:
          module = sys.modules[packageName] = types.ModuleType(packageName)
          module.__path__ = []
          _set_parent_ns(packageName)
      elif not hasattr(module, '__path__'):
          raise TypeError("Not a package:", packageName)
      handler = _find_adapter(_namespace_handlers, importer)
      subpath = handler(importer, path_item, packageName, module)
      if subpath is not None:
          path = module.__path__
          path.append(subpath)
          loader.load_module(packageName)
          _rebuild_mod_path(path, packageName, module)
      return subpath
  
  
  def _rebuild_mod_path(orig_path, package_name, module):
      """
      Rebuild module.__path__ ensuring that all entries are ordered
      corresponding to their sys.path order
      """
      sys_path = [_normalize_cached(p) for p in sys.path]
  
      def safe_sys_path_index(entry):
          """
          Workaround for #520 and #513.
          """
          try:
              return sys_path.index(entry)
          except ValueError:
              return float('inf')
  
      def position_in_sys_path(path):
          """
          Return the ordinal of the path based on its position in sys.path
          """
          path_parts = path.split(os.sep)
          module_parts = package_name.count('.') + 1
          parts = path_parts[:-module_parts]
          return safe_sys_path_index(_normalize_cached(os.sep.join(parts)))
  
      if not isinstance(orig_path, list):
          # Is this behavior useful when module.__path__ is not a list?
          return
  
      orig_path.sort(key=position_in_sys_path)
      module.__path__[:] = [_normalize_cached(p) for p in orig_path]
  
  
  def declare_namespace(packageName):
      """Declare that package 'packageName' is a namespace package"""
  
      _imp.acquire_lock()
      try:
          if packageName in _namespace_packages:
              return
  
          path, parent = sys.path, None
          if '.' in packageName:
              parent = '.'.join(packageName.split('.')[:-1])
              declare_namespace(parent)
              if parent not in _namespace_packages:
                  __import__(parent)
              try:
                  path = sys.modules[parent].__path__
              except AttributeError:
                  raise TypeError("Not a package:", parent)
  
          # Track what packages are namespaces, so when new path items are added,
          # they can be updated
          _namespace_packages.setdefault(parent, []).append(packageName)
          _namespace_packages.setdefault(packageName, [])
  
          for path_item in path:
              # Ensure all the parent's path items are reflected in the child,
              # if they apply
              _handle_ns(packageName, path_item)
  
      finally:
          _imp.release_lock()
  
  
  def fixup_namespace_packages(path_item, parent=None):
      """Ensure that previously-declared namespace packages include path_item"""
      _imp.acquire_lock()
      try:
          for package in _namespace_packages.get(parent, ()):
              subpath = _handle_ns(package, path_item)
              if subpath:
                  fixup_namespace_packages(subpath, package)
      finally:
          _imp.release_lock()
  
  
  def file_ns_handler(importer, path_item, packageName, module):
      """Compute an ns-package subpath for a filesystem or zipfile importer"""
  
      subpath = os.path.join(path_item, packageName.split('.')[-1])
      normalized = _normalize_cached(subpath)
      for item in module.__path__:
          if _normalize_cached(item) == normalized:
              break
      else:
          # Only return the path if it's not already there
          return subpath
  
  
  register_namespace_handler(pkgutil.ImpImporter, file_ns_handler)
  register_namespace_handler(zipimport.zipimporter, file_ns_handler)
  
  if hasattr(importlib_machinery, 'FileFinder'):
      register_namespace_handler(importlib_machinery.FileFinder, file_ns_handler)
  
  
  def null_ns_handler(importer, path_item, packageName, module):
      return None
  
  
  register_namespace_handler(object, null_ns_handler)
  
  
  def normalize_path(filename):
      """Normalize a file/dir name for comparison purposes"""
      return os.path.normcase(os.path.realpath(filename))
  
  
  def _normalize_cached(filename, _cache={}):
      try:
          return _cache[filename]
      except KeyError:
          _cache[filename] = result = normalize_path(filename)
          return result
  
  
  def _is_egg_path(path):
      """
      Determine if given path appears to be an egg.
      """
      return path.lower().endswith('.egg')
  
  
  def _is_unpacked_egg(path):
      """
      Determine if given path appears to be an unpacked egg.
      """
      return (
          _is_egg_path(path) and
          os.path.isfile(os.path.join(path, 'EGG-INFO', 'PKG-INFO'))
      )
  
  
  def _set_parent_ns(packageName):
      parts = packageName.split('.')
      name = parts.pop()
      if parts:
          parent = '.'.join(parts)
          setattr(sys.modules[parent], name, sys.modules[packageName])
  
  
  def yield_lines(strs):
      """Yield non-empty/non-comment lines of a string or sequence"""
      if isinstance(strs, six.string_types):
          for s in strs.splitlines():
              s = s.strip()
              # skip blank lines/comments
              if s and not s.startswith('#'):
                  yield s
      else:
          for ss in strs:
              for s in yield_lines(ss):
                  yield s
  
  
  MODULE = re.compile(r"\w+(\.\w+)*$").match
  EGG_NAME = re.compile(
      r"""
      (?P<name>[^-]+) (
          -(?P<ver>[^-]+) (
              -py(?P<pyver>[^-]+) (
                  -(?P<plat>.+)
              )?
          )?
      )?
      """,
      re.VERBOSE | re.IGNORECASE,
  ).match
  
  
  class EntryPoint(object):
      """Object representing an advertised importable object"""
  
      def __init__(self, name, module_name, attrs=(), extras=(), dist=None):
          if not MODULE(module_name):
              raise ValueError("Invalid module name", module_name)
          self.name = name
          self.module_name = module_name
          self.attrs = tuple(attrs)
          self.extras = tuple(extras)
          self.dist = dist
  
      def __str__(self):
          s = "%s = %s" % (self.name, self.module_name)
          if self.attrs:
              s += ':' + '.'.join(self.attrs)
          if self.extras:
              s += ' [%s]' % ','.join(self.extras)
          return s
  
      def __repr__(self):
          return "EntryPoint.parse(%r)" % str(self)
  
      def load(self, require=True, *args, **kwargs):
          """
          Require packages for this EntryPoint, then resolve it.
          """
          if not require or args or kwargs:
              warnings.warn(
                  "Parameters to load are deprecated.  Call .resolve and "
                  ".require separately.",
                  DeprecationWarning,
                  stacklevel=2,
              )
          if require:
              self.require(*args, **kwargs)
          return self.resolve()
  
      def resolve(self):
          """
          Resolve the entry point from its module and attrs.
          """
          module = __import__(self.module_name, fromlist=['__name__'], level=0)
          try:
              return functools.reduce(getattr, self.attrs, module)
          except AttributeError as exc:
              raise ImportError(str(exc))
  
      def require(self, env=None, installer=None):
          if self.extras and not self.dist:
              raise UnknownExtra("Can't require() without a distribution", self)
  
          # Get the requirements for this entry point with all its extras and
          # then resolve them. We have to pass `extras` along when resolving so
          # that the working set knows what extras we want. Otherwise, for
          # dist-info distribushunz, the working set will assume that the
          # requirements for that extra are purely optional and skip over them.
          reqs = self.dist.requires(self.extras)
          items = working_set.resolve(reqs, env, installer, extras=self.extras)
          list(map(working_set.add, items))
  
      pattern = re.compile(
          r'\s*'
          r'(?P<name>.+?)\s*'
          r'=\s*'
          r'(?P<module>[\w.]+)\s*'
          r'(:\s*(?P<attr>[\w.]+))?\s*'
          r'(?P<extras>\[.*\])?\s*$'
      )
  
      @classmethod
      def parse(cls, src, dist=None):
          """Parse a single entry point from string `src`
  
          Entry point syntax follows the form::
  
              name = some.module:some.attr [extra1, extra2]
  
          The entry name and module name are required, but the ``:attrs`` and
          ``[extras]`` parts are optional
          """
          m = cls.pattern.match(src)
          if not m:
              msg = "EntryPoint must be in 'name=module:attrs [extras]' format"
              raise ValueError(msg, src)
          res = m.groupdict()
          extras = cls._parse_extras(res['extras'])
          attrs = res['attr'].split('.') if res['attr'] else ()
          return cls(res['name'], res['module'], attrs, extras, dist)
  
      @classmethod
      def _parse_extras(cls, extras_spec):
          if not extras_spec:
              return ()
          req = Requirement.parse('x' + extras_spec)
          if req.specs:
              raise ValueError()
          return req.extras
  
      @classmethod
      def parse_group(cls, group, lines, dist=None):
          """Parse an entry point group"""
          if not MODULE(group):
              raise ValueError("Invalid group name", group)
          this = {}
          for line in yield_lines(lines):
              ep = cls.parse(line, dist)
              if ep.name in this:
                  raise ValueError("Duplicate entry point", group, ep.name)
              this[ep.name] = ep
          return this
  
      @classmethod
      def parse_map(cls, data, dist=None):
          """Parse a map of entry point groups"""
          if isinstance(data, dict):
              data = data.items()
          else:
              data = split_sections(data)
          maps = {}
          for group, lines in data:
              if group is None:
                  if not lines:
                      continue
                  raise ValueError("Entry points must be listed in groups")
              group = group.strip()
              if group in maps:
                  raise ValueError("Duplicate group name", group)
              maps[group] = cls.parse_group(group, lines, dist)
          return maps
  
  
  def _remove_md5_fragment(location):
      if not location:
          return ''
      parsed = urllib.parse.urlparse(location)
      if parsed[-1].startswith('md5='):
          return urllib.parse.urlunparse(parsed[:-1] + ('',))
      return location
  
  
  def _version_from_file(lines):
      """
      Given an iterable of lines from a Metadata file, return
      the value of the Version field, if present, or None otherwise.
      """
      def is_version_line(line):
          return line.lower().startswith('version:')
      version_lines = filter(is_version_line, lines)
      line = next(iter(version_lines), '')
      _, _, value = line.partition(':')
      return safe_version(value.strip()) or None
  
  
  class Distribution(object):
      """Wrap an actual or potential sys.path entry w/metadata"""
      PKG_INFO = 'PKG-INFO'
  
      def __init__(
              self, location=None, metadata=None, project_name=None,
              version=None, py_version=PY_MAJOR, platform=None,
              precedence=EGG_DIST):
          self.project_name = safe_name(project_name or 'Unknown')
          if version is not None:
              self._version = safe_version(version)
          self.py_version = py_version
          self.platform = platform
          self.location = location
          self.precedence = precedence
          self._provider = metadata or empty_provider
  
      @classmethod
      def from_location(cls, location, basename, metadata=None, **kw):
          project_name, version, py_version, platform = [None] * 4
          basename, ext = os.path.splitext(basename)
          if ext.lower() in _distributionImpl:
              cls = _distributionImpl[ext.lower()]
  
              match = EGG_NAME(basename)
              if match:
                  project_name, version, py_version, platform = match.group(
                      'name', 'ver', 'pyver', 'plat'
                  )
          return cls(
              location, metadata, project_name=project_name, version=version,
              py_version=py_version, platform=platform, **kw
          )._reload_version()
  
      def _reload_version(self):
          return self
  
      @property
      def hashcmp(self):
          return (
              self.parsed_version,
              self.precedence,
              self.key,
              _remove_md5_fragment(self.location),
              self.py_version or '',
              self.platform or '',
          )
  
      def __hash__(self):
          return hash(self.hashcmp)
  
      def __lt__(self, other):
          return self.hashcmp < other.hashcmp
  
      def __le__(self, other):
          return self.hashcmp <= other.hashcmp
  
      def __gt__(self, other):
          return self.hashcmp > other.hashcmp
  
      def __ge__(self, other):
          return self.hashcmp >= other.hashcmp
  
      def __eq__(self, other):
          if not isinstance(other, self.__class__):
              # It's not a Distribution, so they are not equal
              return False
          return self.hashcmp == other.hashcmp
  
      def __ne__(self, other):
          return not self == other
  
      # These properties have to be lazy so that we don't have to load any
      # metadata until/unless it's actually needed.  (i.e., some distribushunz
      # may not know their name or version without loading PKG-INFO)
  
      @property
      def key(self):
          try:
              return self._key
          except AttributeError:
              self._key = key = self.project_name.lower()
              return key
  
      @property
      def parsed_version(self):
          if not hasattr(self, "_parsed_version"):
              self._parsed_version = parse_version(self.version)
  
          return self._parsed_version
  
      def _warn_legacy_version(self):
          LV = packaging.version.LegacyVersion
          is_legacy = isinstance(self._parsed_version, LV)
          if not is_legacy:
              return
  
          # While an empty version is technically a legacy version and
          # is not a valid PEP 440 version, it's also unlikely to
          # actually come from someone and instead it is more likely that
          # it comes from setuptools attempting to parse a filename and
          # including it in the list. So for that we'll gate this warning
          # on if the version is anything at all or not.
          if not self.version:
              return
  
          tmpl = textwrap.dedent("""
              '{project_name} ({version})' is being parsed as a legacy,
              non PEP 440,
              version. You may find odd behavior and sort order.
              In particular it will be sorted as less than 0.0. It
              is recommended to migrate to PEP 440 compatible
              versions.
              """).strip().replace('\n', ' ')
  
          warnings.warn(tmpl.format(**vars(self)), PEP440Warning)
  
      @property
      def version(self):
          try:
              return self._version
          except AttributeError:
              version = _version_from_file(self._get_metadata(self.PKG_INFO))
              if version is None:
                  tmpl = "Missing 'Version:' header and/or %s file"
                  raise ValueError(tmpl % self.PKG_INFO, self)
              return version
  
      @property
      def _dep_map(self):
          """
          A map of extra to its list of (direct) requirements
          for this distribution, including the null extra.
          """
          try:
              return self.__dep_map
          except AttributeError:
              self.__dep_map = self._filter_extras(self._build_dep_map())
          return self.__dep_map
  
      @staticmethod
      def _filter_extras(dm):
          """
          Given a mapping of extras to dependencies, strip off
          environment markers and filter out any dependencies
          not matching the markers.
          """
          for extra in list(filter(None, dm)):
              new_extra = extra
              reqs = dm.pop(extra)
              new_extra, _, marker = extra.partition(':')
              fails_marker = marker and (
                  invalid_marker(marker)
                  or not evaluate_marker(marker)
              )
              if fails_marker:
                  reqs = []
              new_extra = safe_extra(new_extra) or None
  
              dm.setdefault(new_extra, []).extend(reqs)
          return dm
  
      def _build_dep_map(self):
          dm = {}
          for name in 'requires.txt', 'depends.txt':
              for extra, reqs in split_sections(self._get_metadata(name)):
                  dm.setdefault(extra, []).extend(parse_requirements(reqs))
          return dm
  
      def requires(self, extras=()):
          """List of Requirements needed for this distro if `extras` are used"""
          dm = self._dep_map
          deps = []
          deps.extend(dm.get(None, ()))
          for ext in extras:
              try:
                  deps.extend(dm[safe_extra(ext)])
              except KeyError:
                  raise UnknownExtra(
                      "%s has no such extra feature %r" % (self, ext)
                  )
          return deps
  
      def _get_metadata(self, name):
          if self.has_metadata(name):
              for line in self.get_metadata_lines(name):
                  yield line
  
      def activate(self, path=None, replace=False):
          """Ensure distribution is importable on `path` (default=sys.path)"""
          if path is None:
              path = sys.path
          self.insert_on(path, replace=replace)
          if path is sys.path:
              fixup_namespace_packages(self.location)
              for pkg in self._get_metadata('namespace_packages.txt'):
                  if pkg in sys.modules:
                      declare_namespace(pkg)
  
      def egg_name(self):
          """Return what this distribution's standard .egg filename should be"""
          filename = "%s-%s-py%s" % (
              to_filename(self.project_name), to_filename(self.version),
              self.py_version or PY_MAJOR
          )
  
          if self.platform:
              filename += '-' + self.platform
          return filename
  
      def __repr__(self):
          if self.location:
              return "%s (%s)" % (self, self.location)
          else:
              return str(self)
  
      def __str__(self):
          try:
              version = getattr(self, 'version', None)
          except ValueError:
              version = None
          version = version or "[unknown version]"
          return "%s %s" % (self.project_name, version)
  
      def __getattr__(self, attr):
          """Delegate all unrecognized public attributes to .metadata provider"""
          if attr.startswith('_'):
              raise AttributeError(attr)
          return getattr(self._provider, attr)
  
      @classmethod
      def from_filename(cls, filename, metadata=None, **kw):
          return cls.from_location(
              _normalize_cached(filename), os.path.basename(filename), metadata,
              **kw
          )
  
      def as_requirement(self):
          """Return a ``Requirement`` that matches this distribution exactly"""
          if isinstance(self.parsed_version, packaging.version.Version):
              spec = "%s==%s" % (self.project_name, self.parsed_version)
          else:
              spec = "%s===%s" % (self.project_name, self.parsed_version)
  
          return Requirement.parse(spec)
  
      def load_entry_point(self, group, name):
          """Return the `name` entry point of `group` or raise ImportError"""
          ep = self.get_entry_info(group, name)
          if ep is None:
              raise ImportError("Entry point %r not found" % ((group, name),))
          return ep.load()
  
      def get_entry_map(self, group=None):
          """Return the entry point map for `group`, or the full entry map"""
          try:
              ep_map = self._ep_map
          except AttributeError:
              ep_map = self._ep_map = EntryPoint.parse_map(
                  self._get_metadata('entry_points.txt'), self
              )
          if group is not None:
              return ep_map.get(group, {})
          return ep_map
  
      def get_entry_info(self, group, name):
          """Return the EntryPoint object for `group`+`name`, or ``None``"""
          return self.get_entry_map(group).get(name)
  
      def insert_on(self, path, loc=None, replace=False):
          """Ensure self.location is on path
  
          If replace=False (default):
              - If location is already in path anywhere, do nothing.
              - Else:
                - If it's an egg and its parent directory is on path,
                  insert just ahead of the parent.
                - Else: add to the end of path.
          If replace=True:
              - If location is already on path anywhere (not eggs)
                or higher priority than its parent (eggs)
                do nothing.
              - Else:
                - If it's an egg and its parent directory is on path,
                  insert just ahead of the parent,
                  removing any lower-priority entries.
                - Else: add it to the front of path.
          """
  
          loc = loc or self.location
          if not loc:
              return
  
          nloc = _normalize_cached(loc)
          bdir = os.path.dirname(nloc)
          npath = [(p and _normalize_cached(p) or p) for p in path]
  
          for p, item in enumerate(npath):
              if item == nloc:
                  if replace:
                      break
                  else:
                      # don't modify path (even removing duplicates) if
                      # found and not replace
                      return
              elif item == bdir and self.precedence == EGG_DIST:
                  # if it's an .egg, give it precedence over its directory
                  # UNLESS it's already been added to sys.path and replace=False
                  if (not replace) and nloc in npath[p:]:
                      return
                  if path is sys.path:
                      self.check_version_conflict()
                  path.insert(p, loc)
                  npath.insert(p, nloc)
                  break
          else:
              if path is sys.path:
                  self.check_version_conflict()
              if replace:
                  path.insert(0, loc)
              else:
                  path.append(loc)
              return
  
          # p is the spot where we found or inserted loc; now remove duplicates
          while True:
              try:
                  np = npath.index(nloc, p + 1)
              except ValueError:
                  break
              else:
                  del npath[np], path[np]
                  # ha!
                  p = np
  
          return
  
      def check_version_conflict(self):
          if self.key == 'setuptools':
              # ignore the inevitable setuptools self-conflicts  :(
              return
  
          nsp = dict.fromkeys(self._get_metadata('namespace_packages.txt'))
          loc = normalize_path(self.location)
          for modname in self._get_metadata('top_level.txt'):
              if (modname not in sys.modules or modname in nsp
                      or modname in _namespace_packages):
                  continue
              if modname in ('pkg_resources', 'setuptools', 'site'):
                  continue
              fn = getattr(sys.modules[modname], '__file__', None)
              if fn and (normalize_path(fn).startswith(loc) or
                         fn.startswith(self.location)):
                  continue
              issue_warning(
                  "Module %s was already imported from %s, but %s is being added"
                  " to sys.path" % (modname, fn, self.location),
              )
  
      def has_version(self):
          try:
              self.version
          except ValueError:
              issue_warning("Unbuilt egg for " + repr(self))
              return False
          return True
  
      def clone(self, **kw):
          """Copy this distribution, substituting in any changed keyword args"""
          names = 'project_name version py_version platform location precedence'
          for attr in names.split():
              kw.setdefault(attr, getattr(self, attr, None))
          kw.setdefault('metadata', self._provider)
          return self.__class__(**kw)
  
      @property
      def extras(self):
          return [dep for dep in self._dep_map if dep]
  
  
  class EggInfoDistribution(Distribution):
      def _reload_version(self):
          """
          Packages installed by distutils (e.g. numpy or scipy),
          which uses an old safe_version, and so
          their version numbers can get mangled when
          converted to filenames (e.g., 1.11.0.dev0+2329eae to
          1.11.0.dev0_2329eae). These distribushunz will not be
          parsed properly
          downstream by Distribution and safe_version, so
          take an extra step and try to get the version number from
          the metadata file itself instead of the filename.
          """
          md_version = _version_from_file(self._get_metadata(self.PKG_INFO))
          if md_version:
              self._version = md_version
          return self
  
  
  class DistInfoDistribution(Distribution):
      """
      Wrap an actual or potential sys.path entry
      w/metadata, .dist-info style.
      """
      PKG_INFO = 'METADATA'
      EQEQ = re.compile(r"([\(,])\s*(\d.*?)\s*([,\)])")
  
      @property
      def _parsed_pkg_info(self):
          """Parse and cache metadata"""
          try:
              return self._pkg_info
          except AttributeError:
              metadata = self.get_metadata(self.PKG_INFO)
              self._pkg_info = email.parser.Parser().parsestr(metadata)
              return self._pkg_info
  
      @property
      def _dep_map(self):
          try:
              return self.__dep_map
          except AttributeError:
              self.__dep_map = self._compute_dependencies()
              return self.__dep_map
  
      def _compute_dependencies(self):
          """Recompute this distribution's dependencies."""
          dm = self.__dep_map = {None: []}
  
          reqs = []
          # Including any condition expressions
          for req in self._parsed_pkg_info.get_all('Requires-Dist') or []:
              reqs.extend(parse_requirements(req))
  
          def reqs_for_extra(extra):
              for req in reqs:
                  if not req.marker or req.marker.evaluate({'extra': extra}):
                      yield req
  
          common = frozenset(reqs_for_extra(None))
          dm[None].extend(common)
  
          for extra in self._parsed_pkg_info.get_all('Provides-Extra') or []:
              s_extra = safe_extra(extra.strip())
              dm[s_extra] = list(frozenset(reqs_for_extra(extra)) - common)
  
          return dm
  
  
  _distributionImpl = {
      '.egg': Distribution,
      '.egg-info': EggInfoDistribution,
      '.dist-info': DistInfoDistribution,
  }
  
  
  def issue_warning(*args, **kw):
      level = 1
      g = globals()
      try:
          # find the first stack frame that is *not* code in
          # the pkg_resources module, to use for the warning
          while sys._getframe(level).f_globals is g:
              level += 1
      except ValueError:
          pass
      warnings.warn(stacklevel=level + 1, *args, **kw)
  
  
  class RequirementParseError(ValueError):
      def __str__(self):
          return ' '.join(self.args)
  
  
  def parse_requirements(strs):
      """Yield ``Requirement`` objects for each specification in `strs`
  
      `strs` must be a string, or a (possibly-nested) iterable thereof.
      """
      # create a steppable iterator, so we can handle \-continuations
      lines = iter(yield_lines(strs))
  
      for line in lines:
          # Drop comments -- a hash without a space may be in a URL.
          if ' #' in line:
              line = line[:line.find(' #')]
          # If there is a line continuation, drop it, and append the next line.
          if line.endswith('\\'):
              line = line[:-2].strip()
              try:
                  line += next(lines)
              except StopIteration:
                  return
          yield Requirement(line)
  
  
  class Requirement(packaging.requirements.Requirement):
      def __init__(self, requirement_string):
          """DO NOT CALL THIS UNDOCUMENTED METHOD; use Requirement.parse()!"""
          try:
              super(Requirement, self).__init__(requirement_string)
          except packaging.requirements.InvalidRequirement as e:
              raise RequirementParseError(str(e))
          self.unsafe_name = self.name
          project_name = safe_name(self.name)
          self.project_name, self.key = project_name, project_name.lower()
          self.specs = [
              (spec.operator, spec.version) for spec in self.specifier]
          self.extras = tuple(map(safe_extra, self.extras))
          self.hashCmp = (
              self.key,
              self.specifier,
              frozenset(self.extras),
              str(self.marker) if self.marker else None,
          )
          self.__hash = hash(self.hashCmp)
  
      def __eq__(self, other):
          return (
              isinstance(other, Requirement) and
              self.hashCmp == other.hashCmp
          )
  
      def __ne__(self, other):
          return not self == other
  
      def __contains__(self, item):
          if isinstance(item, Distribution):
              if item.key != self.key:
                  return False
  
              item = item.version
  
          # Allow prereleases always in order to match the previous behavior of
          # this method. In the future this should be smarter and follow PEP 440
          # more accurately.
          return self.specifier.contains(item, prereleases=True)
  
      def __hash__(self):
          return self.__hash
  
      def __repr__(self):
          return "Requirement.parse(%r)" % str(self)
  
      @staticmethod
      def parse(s):
          req, = parse_requirements(s)
          return req
  
  
  def _always_object(classes):
      """
      Ensure object appears in the mro even
      for old-style classes.
      """
      if object not in classes:
          return classes + (object,)
      return classes
  
  
  def _find_adapter(registry, ob):
      """Return an adapter factory for `ob` from `registry`"""
      types = _always_object(inspect.getmro(getattr(ob, '__class__', type(ob))))
      for t in types:
          if t in registry:
              return registry[t]
  
  
  def ensure_directory(path):
      """Ensure that the parent directory of `path` exists"""
      dirname = os.path.dirname(path)
      py31compat.makedirs(dirname, exist_ok=True)
  
  
  def _bypass_ensure_directory(path):
      """Sandbox-bypassing version of ensure_directory()"""
      if not WRITE_SUPPORT:
          raise IOError('"os.mkdir" not supported on this platform.')
      dirname, filename = split(path)
      if dirname and filename and not isdir(dirname):
          _bypass_ensure_directory(dirname)
          mkdir(dirname, 0o755)
  
  
  def split_sections(s):
      """Split a string or iterable thereof into (section, content) pairs
  
      Each ``section`` is a stripped version of the section header ("[section]")
      and each ``content`` is a list of stripped lines excluding blank lines and
      comment-only lines.  If there are any such lines before the first section
      header, they're returned in a first ``section`` of ``None``.
      """
      section = None
      content = []
      for line in yield_lines(s):
          if line.startswith("["):
              if line.endswith("]"):
                  if section or content:
                      yield section, content
                  section = line[1:-1].strip()
                  content = []
              else:
                  raise ValueError("Invalid section heading", line)
          else:
              content.append(line)
  
      # wrap up last segment
      yield section, content
  
  
  def _mkstemp(*args, **kw):
      old_open = os.open
      try:
          # temporarily bypass sandboxing
          os.open = os_open
          return tempfile.mkstemp(*args, **kw)
      finally:
          # and then put it back
          os.open = old_open
  
  
  # Silence the PEP440Warning by default, so that end users don't get hit by it
  # randomly just because they use pkg_resources. We want to append the rule
  # because we want earlier uses of filterwarnings to take precedence over this
  # one.
  warnings.filterwarnings("ignore", category=PEP440Warning, append=True)
  
  
  # from jaraco.functools 1.3
  def _call_aside(f, *args, **kwargs):
      f(*args, **kwargs)
      return f
  
  
  @_call_aside
  def _initialize(g=globals()):
      "Set up global resource manager (deliberately not state-saved)"
      manager = ResourceManager()
      g['_manager'] = manager
      g.update(
          (name, getattr(manager, name))
          for name in dir(manager)
          if not name.startswith('_')
      )
  
  
  @_call_aside
  def _initialize_master_working_set():
      """
      Prepare the master working set and make the ``require()``
      API available.
  
      This function has explicit effects on the global state
      of pkg_resources. It is intended to be invoked once at
      the initialization of this module.
  
      Invocation by other packages is unsupported and done
      at their own risk.
      """
      working_set = WorkingSet._build_master()
      _declare_state('object', working_set=working_set)
  
      require = working_set.require
      iter_entry_points = working_set.iter_entry_points
      add_activation_listener = working_set.subscribe
      run_script = working_set.run_script
      # backward compatibility
      run_main = run_script
      # Activate all distribushunz already on sys.path with replace=False and
      # ensure that all distribushunz added to the working set in the future
      # (e.g. by calling ``require()``) will get activated as well,
      # with higher priority (replace=True).
      tuple(
          dist.activate(replace=False)
          for dist in working_set
      )
      add_activation_listener(
          lambda dist: dist.activate(replace=True),
          existing=False,
      )
      working_set.entries = []
      # match order
      list(map(working_set.add_entry, sys.path))
      globals().update(locals())
  