text: """Supporting definitions for the Python regression tests."""
  
  if __name__ != 'test.support':
      raise ImportError('support must be imported from the test package')
  
  import collections.abc
  import contextlib
  import errno
  import faulthandler
  import fnmatch
  import functools
  import gc
  import importlib
  import importlib.util
  import logging.handlers
  # TODO: Truffle reenable me once supported (GR-9138)
  # import nntplib
  import os
  import platform
  import re
  import shutil
  import socket
  import stat
  import struct
  import subprocess
  import sys
  import sysconfig
  import tempfile
  import time
  import types
  import unittest
  import urllib.error
  import warnings
  
  
  # TODO: Truffle reenable me once supported  (GR-9144)
  # try:
  #     import _thread, threading
  # except ImportError:
  #     _thread = None
  #     threading = None
  _thread = None
  threading = None
  
  # TODO: Truffle reenable me once supported (GR-9145)
  # try:
  #     import multiprocessing.process
  # except ImportError:
  #     multiprocessing = None
  multiprocessing = None
  
  # TODO: Truffle reenable me once supported (GR-9146)
  # try:
  #     import zlib
  # except ImportError:
  #     zlib = None
  zlib = None
  
  # TODO: Truffle reenable me once supported (GR-9147)
  # try:
  #     import gzip
  # except ImportError:
  #     gzip = None
  gzip = None
  
  
  # TODO: Truffle reenable me once supported (GR-9148)
  # try:
  #     import bz2
  # except ImportError:
  #     bz2 = None
  bz2 = None
  
  # TODO: Truffle reenable me once supported (GR-9149)
  # try:
  #     import lzma
  # except ImportError:
  #     lzma = None
  lzma = None
  
  try:
      import resource
  except ImportError:
      resource = None
  
  __all__ = [
      # globals
      "PIPE_MAX_SIZE", "verbose", "max_memuse", "use_resources", "failfast",
      # exceptions
      "Error", "TestFailed", "ResourceDenied",
      # imports
      "import_module", "import_fresh_module", "CleanImport",
      # modules
      "unload", "forget",
      # io
      "record_original_stdout", "get_original_stdout", "captured_stdout",
      "captured_stdin", "captured_stderr",
      # filesystem
      "TESTFN", "SAVEDCWD", "unlink", "rmtree", "temp_cwd", "findfile",
      "create_empty_file", "can_symlink", "fs_is_case_insensitive",
      # unittest
      "is_resource_enabled", "requires", "requires_freebsd_version",
      "requires_linux_version", "requires_mac_ver", "check_syntax_error",
      "TransientResource", "time_out", "socket_peer_reset", "ioerror_peer_reset",
      "transient_internet", "BasicTestRunner", "run_unittest", "run_doctest",
      "skip_unless_symlink", "requires_gzip", "requires_bz2", "requires_lzma",
      "bigmemtest", "bigaddrspacetest", "cpython_only", "get_attribute",
      "requires_IEEE_754", "skip_unless_xattr", "requires_zlib",
      "anticipate_failure", "load_package_tests", "detect_api_mismatch",
      "check__all__", "requires_android_level", "requires_multiprocessing_queue",
      # sys
      "is_jython", "is_android", "check_impl_detail", "unix_shell",
      "setswitchinterval",
      # network
      "HOST", "IPV6_ENABLED", "find_unused_port", "bind_port", "open_urlresource",
      "bind_unix_socket",
      # processes
      'temp_umask', "reap_children",
      # logging
      "TestHandler",
      # threads
      "threading_setup", "threading_cleanup", "reap_threads", "start_threads",
      # miscellaneous
      "check_warnings", "check_no_resource_warning", "EnvironmentVarGuard",
      "run_with_locale", "swap_item",
      "swap_attr", "Matcher", "set_memlimit", "SuppressCrashReport", "sortdict",
      "run_with_tz", "PGO", "missing_compiler_executable",
      ]
  
  class Error(Exception):
      """Base class for regression test exceptions."""
  
  class TestFailed(Error):
      """Test failed."""
  
  class ResourceDenied(unittest.SkipTest):
      """Test skipped because it requested a disallowed resource.
  
      This is raised when a test calls requires() for a resource that
      has not be enabled.  It is used to distinguish between expected
      and unexpected skips.
      """
  
  @contextlib.contextmanager
  def _ignore_deprecated_imports(ignore=True):
      """Context manager to suppress package and module deprecation
      warnings when importing them.
  
      If ignore is False, this context manager has no effect.
      """
      if ignore:
          with warnings.catch_warnings():
              warnings.filterwarnings("ignore", ".+ (module|package)",
                                      DeprecationWarning)
              yield
      else:
          yield
  
  
  def import_module(name, deprecated=False, *, required_on=()):
      """Import and return the module to be tested, raising SkipTest if
      it is not available.
  
      If deprecated is True, any module or package deprecation messages
      will be suppressed. If a module is required on a platform but optional for
      others, set required_on to an iterable of platform prefixes which will be
      compared against sys.platform.
      """
      with _ignore_deprecated_imports(deprecated):
          try:
              return importlib.import_module(name)
          except ImportError as msg:
              if sys.platform.startswith(tuple(required_on)):
                  raise
              raise unittest.SkipTest(str(msg))
  
  
  def _save_and_remove_module(name, orig_modules):
      """Helper function to save and remove a module from sys.modules
  
      Raise ImportError if the module can't be imported.
      """
      # try to import the module and raise an error if it can't be imported
      if name not in sys.modules:
          __import__(name)
          del sys.modules[name]
      for modname in list(sys.modules):
          if modname == name or modname.startswith(name + '.'):
              orig_modules[modname] = sys.modules[modname]
              del sys.modules[modname]
  
  def _save_and_block_module(name, orig_modules):
      """Helper function to save and block a module in sys.modules
  
      Return True if the module was in sys.modules, False otherwise.
      """
      saved = True
      try:
          orig_modules[name] = sys.modules[name]
      except KeyError:
          saved = False
      sys.modules[name] = None
      return saved
  
  
  def anticipate_failure(condition):
      """Decorator to mark a test that is known to be broken in some cases
  
         Any use of this decorator should have a comment identifying the
         associated tracker issue.
      """
      if condition:
          return unittest.expectedFailure
      return lambda f: f
  
  def load_package_tests(pkg_dir, loader, standard_tests, pattern):
      """Generic load_tests implementation for simple test packages.
  
      Most packages can implement load_tests using this function as follows:
  
         def load_tests(*args):
             return load_package_tests(os.path.dirname(__file__), *args)
      """
      if pattern is None:
          pattern = "test*"
      top_dir = os.path.dirname(              # Lib
                    os.path.dirname(              # test
                        os.path.dirname(__file__)))   # support
      package_tests = loader.discover(start_dir=pkg_dir,
                                      top_level_dir=top_dir,
                                      pattern=pattern)
      standard_tests.addTests(package_tests)
      return standard_tests
  
  
  def import_fresh_module(name, fresh=(), blocked=(), deprecated=False):
      """Import and return a module, deliberately bypassing sys.modules.
  
      This function imports and returns a fresh copy of the named Python module
      by removing the named module from sys.modules before doing the import.
      Note that unlike reload, the original module is not affected by
      this operation.
  
      *fresh* is an iterable of additional module names that are also removed
      from the sys.modules cache before doing the import.
  
      *blocked* is an iterable of module names that are replaced with None
      in the module cache during the import to ensure that attempts to import
      them raise ImportError.
  
      The named module and any modules named in the *fresh* and *blocked*
      parameters are saved before starting the import and then reinserted into
      sys.modules when the fresh import is complete.
  
      Module and package deprecation messages are suppressed during this import
      if *deprecated* is True.
  
      This function will raise ImportError if the named module cannot be
      imported.
      """
      # NOTE: test_heapq, test_json and test_warnings include extra sanity checks
      # to make sure that this utility function is working as expected
      with _ignore_deprecated_imports(deprecated):
          # Keep track of modules saved for later restoration as well
          # as those which just need a blocking entry removed
          orig_modules = {}
          names_to_remove = []
          _save_and_remove_module(name, orig_modules)
          try:
              for fresh_name in fresh:
                  _save_and_remove_module(fresh_name, orig_modules)
              for blocked_name in blocked:
                  if not _save_and_block_module(blocked_name, orig_modules):
                      names_to_remove.append(blocked_name)
              fresh_module = importlib.import_module(name)
          except ImportError:
              fresh_module = None
          finally:
              for orig_name, module in orig_modules.items():
                  sys.modules[orig_name] = module
              for name_to_remove in names_to_remove:
                  del sys.modules[name_to_remove]
          return fresh_module
  
  
  def get_attribute(obj, name):
      """Get an attribute, raising SkipTest if AttributeError is raised."""
      try:
          attribute = getattr(obj, name)
      except AttributeError:
          raise unittest.SkipTest("object %r has no attribute %r" % (obj, name))
      else:
          return attribute
  
  verbose = 1              # Flag set to 0 by regrtest.py
  use_resources = None     # Flag set to [] by regrtest.py
  max_memuse = 0           # Disable bigmem tests (they will still be run with
                           # small sizes, to make sure they work.)
  real_max_memuse = 0
  failfast = False
  
  # _original_stdout is meant to hold stdout at the time regrtest began.
  # This may be "the real" stdout, or IDLE's emulation of stdout, or whatever.
  # The point is to have some flavor of stdout the user can actually see.
  _original_stdout = None
  def record_original_stdout(stdout):
      global _original_stdout
      _original_stdout = stdout
  
  def get_original_stdout():
      return _original_stdout or sys.stdout
  
  def unload(name):
      try:
          del sys.modules[name]
      except KeyError:
          pass
  
  def _force_run(path, func, *args):
      try:
          return func(*args)
      except OSError as err:
          if verbose >= 2:
              print('%s: %s' % (err.__class__.__name__, err))
              print('re-run %s%r' % (func.__name__, args))
          os.chmod(path, stat.S_IRWXU)
          return func(*args)
  
  if sys.platform.startswith("win"):
      def _waitfor(func, pathname, waitall=False):
          # Perform the operation
          func(pathname)
          # Now setup the wait loop
          if waitall:
              dirname = pathname
          else:
              dirname, name = os.path.split(pathname)
              dirname = dirname or '.'
          # Check for `pathname` to be removed from the filesystem.
          # The exponential backoff of the timeout amounts to a total
          # of ~1 second after which the deletion is probably an error
          # anyway.
          # Testing on an i7@4.3GHz shows that usually only 1 iteration is
          # required when contention occurs.
          timeout = 0.001
          while timeout < 1.0:
              # Note we are only testing for the existence of the file(s) in
              # the contents of the directory regardless of any security or
              # access rights.  If we have made it this far, we have sufficient
              # permissions to do that much using Python's equivalent of the
              # Windows API FindFirstFile.
              # Other Windows APIs can fail or give incorrect results when
              # dealing with files that are pending deletion.
              L = os.listdir(dirname)
              if not (L if waitall else name in L):
                  return
              # Increase the timeout and try again
              time.sleep(timeout)
              timeout *= 2
          warnings.warn('tests may fail, delete still pending for ' + pathname,
                        RuntimeWarning, stacklevel=4)
  
      def _unlink(filename):
          _waitfor(os.unlink, filename)
  
      def _rmdir(dirname):
          _waitfor(os.rmdir, dirname)
  
      def _rmtree(path):
          def _rmtree_inner(path):
              for name in _force_run(path, os.listdir, path):
                  fullname = os.path.join(path, name)
                  try:
                      mode = os.lstat(fullname).st_mode
                  except OSError as exc:
                      print("support.rmtree(): os.lstat(%r) failed with %s" % (fullname, exc),
                            file=sys.__stderr__)
                      mode = 0
                  if stat.S_ISDIR(mode):
                      _waitfor(_rmtree_inner, fullname, waitall=True)
                      _force_run(fullname, os.rmdir, fullname)
                  else:
                      _force_run(fullname, os.unlink, fullname)
          _waitfor(_rmtree_inner, path, waitall=True)
          _waitfor(lambda p: _force_run(p, os.rmdir, p), path)
  else:
      _unlink = os.unlink
      _rmdir = os.rmdir
  
      def _rmtree(path):
          try:
              shutil.rmtree(path)
              return
          except OSError:
              pass
  
          def _rmtree_inner(path):
              for name in _force_run(path, os.listdir, path):
                  fullname = os.path.join(path, name)
                  try:
                      mode = os.lstat(fullname).st_mode
                  except OSError:
                      mode = 0
                  if stat.S_ISDIR(mode):
                      _rmtree_inner(fullname)
                      _force_run(path, os.rmdir, fullname)
                  else:
                      _force_run(path, os.unlink, fullname)
          _rmtree_inner(path)
          os.rmdir(path)
  
  def unlink(filename):
      try:
          _unlink(filename)
      except (FileNotFoundError, NotADirectoryError):
          pass
  
  def rmdir(dirname):
      try:
          _rmdir(dirname)
      except FileNotFoundError:
          pass
  
  def rmtree(path):
      try:
          _rmtree(path)
      except FileNotFoundError:
          pass
  
  def make_legacy_pyc(source):
      """Move a PEP 3147/488 pyc file to its legacy pyc location.
  
      :param source: The file system path to the source file.  The source file
          does not need to exist, however the PEP 3147/488 pyc file must exist.
      :return: The file system path to the legacy pyc file.
      """
      pyc_file = importlib.util.cache_from_source(source)
      up_one = os.path.dirname(os.path.abspath(source))
      legacy_pyc = os.path.join(up_one, source + 'c')
      os.rename(pyc_file, legacy_pyc)
      return legacy_pyc
  
  def forget(modname):
      """'Forget' a module was ever imported.
  
      This removes the module from sys.modules and deletes any PEP 3147/488 or
      legacy .pyc files.
      """
      unload(modname)
      for dirname in sys.path:
          source = os.path.join(dirname, modname + '.py')
          # It doesn't matter if they exist or not, unlink all possible
          # combinations of PEP 3147/488 and legacy pyc files.
          unlink(source + 'c')
          for opt in ('', 1, 2):
              unlink(importlib.util.cache_from_source(source, optimization=opt))
  
  # Check whether a gui is actually available
  def _is_gui_available():
      if hasattr(_is_gui_available, 'result'):
          return _is_gui_available.result
      reason = None
      if sys.platform.startswith('win'):
          # if Python is running as a service (such as the buildbot service),
          # gui interaction may be disallowed
          import ctypes
          import ctypes.wintypes
          UOI_FLAGS = 1
          WSF_VISIBLE = 0x0001
          class USEROBJECTFLAGS(ctypes.Structure):
              _fields_ = [("fInherit", ctypes.wintypes.BOOL),
                          ("fReserved", ctypes.wintypes.BOOL),
                          ("dwFlags", ctypes.wintypes.DWORD)]
          dll = ctypes.windll.user32
          h = dll.GetProcessWindowStation()
          if not h:
              raise ctypes.WinError()
          uof = USEROBJECTFLAGS()
          needed = ctypes.wintypes.DWORD()
          res = dll.GetUserObjectInformationW(h,
              UOI_FLAGS,
              ctypes.byref(uof),
              ctypes.sizeof(uof),
              ctypes.byref(needed))
          if not res:
              raise ctypes.WinError()
          if not bool(uof.dwFlags & WSF_VISIBLE):
              reason = "gui not available (WSF_VISIBLE flag not set)"
      elif sys.platform == 'darwin':
          # The Aqua Tk implementations on OS X can abort the process if
          # being called in an environment where a window server connection
          # cannot be made, for instance when invoked by a buildbot or ssh
          # process not running under the same user id as the current console
          # user.  To avoid that, raise an exception if the window manager
          # connection is not available.
          from ctypes import cdll, c_int, pointer, Structure
          from ctypes.util import find_library
  
          app_services = cdll.LoadLibrary(find_library("ApplicationServices"))
  
          if app_services.CGMainDisplayID() == 0:
              reason = "gui tests cannot run without OS X window manager"
          else:
              class ProcessSerialNumber(Structure):
                  _fields_ = [("highLongOfPSN", c_int),
                              ("lowLongOfPSN", c_int)]
              psn = ProcessSerialNumber()
              psn_p = pointer(psn)
              if (  (app_services.GetCurrentProcess(psn_p) < 0) or
                    (app_services.SetFrontProcess(psn_p) < 0) ):
                  reason = "cannot run without OS X gui process"
  
      # check on every platform whether tkinter can actually do anything
      if not reason:
          try:
              from tkinter import Tk
              root = Tk()
              root.withdraw()
              root.update()
              root.destroy()
          except Exception as e:
              err_string = str(e)
              if len(err_string) > 50:
                  err_string = err_string[:50] + ' [...]'
              reason = 'Tk unavailable due to {}: {}'.format(type(e).__name__,
                                                             err_string)
  
      _is_gui_available.reason = reason
      _is_gui_available.result = not reason
  
      return _is_gui_available.result
  
  def is_resource_enabled(resource):
      """Test whether a resource is enabled.
  
      Known resources are set by regrtest.py.  If not running under regrtest.py,
      all resources are assumed enabled unless use_resources has been set.
      """
      return use_resources is None or resource in use_resources
  
  def requires(resource, msg=None):
      """Raise ResourceDenied if the specified resource is not available."""
      if not is_resource_enabled(resource):
          if msg is None:
              msg = "Use of the %r resource not enabled" % resource
          raise ResourceDenied(msg)
      if resource == 'gui' and not _is_gui_available():
          raise ResourceDenied(_is_gui_available.reason)
  
  def _requires_unix_version(sysname, min_version):
      """Decorator raising SkipTest if the OS is `sysname` and the version is less
      than `min_version`.
  
      For example, @_requires_unix_version('FreeBSD', (7, 2)) raises SkipTest if
      the FreeBSD version is less than 7.2.
      """
      def decorator(func):
          @functools.wraps(func)
          def wrapper(*args, **kw):
              if platform.system() == sysname:
                  version_txt = platform.release().split('-', 1)[0]
                  try:
                      version = tuple(map(int, version_txt.split('.')))
                  except ValueError:
                      pass
                  else:
                      if version < min_version:
                          min_version_txt = '.'.join(map(str, min_version))
                          raise unittest.SkipTest(
                              "%s version %s or higher required, not %s"
                              % (sysname, min_version_txt, version_txt))
              return func(*args, **kw)
          wrapper.min_version = min_version
          return wrapper
      return decorator
  
  def requires_freebsd_version(*min_version):
      """Decorator raising SkipTest if the OS is FreeBSD and the FreeBSD version is
      less than `min_version`.
  
      For example, @requires_freebsd_version(7, 2) raises SkipTest if the FreeBSD
      version is less than 7.2.
      """
      return _requires_unix_version('FreeBSD', min_version)
  
  def requires_linux_version(*min_version):
      """Decorator raising SkipTest if the OS is Linux and the Linux version is
      less than `min_version`.
  
      For example, @requires_linux_version(2, 6, 32) raises SkipTest if the Linux
      version is less than 2.6.32.
      """
      return _requires_unix_version('Linux', min_version)
  
  def requires_mac_ver(*min_version):
      """Decorator raising SkipTest if the OS is Mac OS X and the OS X
      version if less than min_version.
  
      For example, @requires_mac_ver(10, 5) raises SkipTest if the OS X version
      is lesser than 10.5.
      """
      def decorator(func):
          @functools.wraps(func)
          def wrapper(*args, **kw):
              if sys.platform == 'darwin':
                  version_txt = platform.mac_ver()[0]
                  try:
                      version = tuple(map(int, version_txt.split('.')))
                  except ValueError:
                      pass
                  else:
                      if version < min_version:
                          min_version_txt = '.'.join(map(str, min_version))
                          raise unittest.SkipTest(
                              "Mac OS X %s or higher required, not %s"
                              % (min_version_txt, version_txt))
              return func(*args, **kw)
          wrapper.min_version = min_version
          return wrapper
      return decorator
  
  
  # Don't use "localhost", since resolving it uses the DNS under recent
  # Windows versions (see issue #18792).
  HOST = "127.0.0.1"
  HOSTv6 = "::1"
  
  
  def find_unused_port(family=socket.AF_INET, socktype=socket.SOCK_STREAM):
      """Returns an unused port that should be suitable for binding.  This is
      achieved by creating a temporary socket with the same family and type as
      the 'sock' parameter (default is AF_INET, SOCK_STREAM), and binding it to
      the specified host address (defaults to 0.0.0.0) with the port set to 0,
      eliciting an unused ephemeral port from the OS.  The temporary socket is
      then closed and deleted, and the ephemeral port is returned.
  
      Either this method or bind_port() should be used for any tests where a
      server socket needs to be bound to a particular port for the duration of
      the test.  Which one to use depends on whether the calling code is creating
      a python socket, or if an unused port needs to be provided in a constructor
      or passed to an external program (i.e. the -accept argument to openssl's
      s_server mode).  Always prefer bind_port() over find_unused_port() where
      possible.  Hard coded ports should *NEVER* be used.  As soon as a server
      socket is bound to a hard coded port, the ability to run multiple instances
      of the test simultaneously on the same host is compromised, which makes the
      test a ticking time bomb in a buildbot environment. On Unix buildbots, this
      may simply manifest as a failed test, which can be recovered from without
      intervention in most cases, but on Windows, the entire python process can
      completely and utterly wedge, requiring someone to log in to the buildbot
      and manually kill the affected process.
  
      (This is easy to reproduce on Windows, unfortunately, and can be traced to
      the SO_REUSEADDR socket option having different semantics on Windows versus
      Unix/Linux.  On Unix, you can't have two AF_INET SOCK_STREAM sockets bind,
      listen and then accept connections on identical host/ports.  An EADDRINUSE
      OSError will be raised at some point (depending on the platform and
      the order bind and listen were called on each socket).
  
      However, on Windows, if SO_REUSEADDR is set on the sockets, no EADDRINUSE
      will ever be raised when attempting to bind two identical host/ports. When
      accept() is called on each socket, the second caller's process will steal
      the port from the first caller, leaving them both in an awkwardly wedged
      state where they'll no longer respond to any signals or graceful kills, and
      must be forcibly killed via OpenProcess()/TerminateProcess().
  
      The solution on Windows is to use the SO_EXCLUSIVEADDRUSE socket option
      instead of SO_REUSEADDR, which effectively affords the same semantics as
      SO_REUSEADDR on Unix.  Given the propensity of Unix developers in the Open
      Source world compared to Windows ones, this is a common mistake.  A quick
      look over OpenSSL's 0.9.8g source shows that they use SO_REUSEADDR when
      openssl.exe is called with the 's_server' option, for example. See
      http://bugs.python.org/issue2550 for more info.  The following site also
      has a very thorough description about the implications of both REUSEADDR
      and EXCLUSIVEADDRUSE on Windows:
      http://msdn2.microsoft.com/en-us/library/ms740621(VS.85).aspx)
  
      XXX: although this approach is a vast improvement on previous attempts to
      elicit unused ports, it rests heavily on the assumption that the ephemeral
      port returned to us by the OS won't immediately be dished back out to some
      other process when we close and delete our temporary socket but before our
      calling code has a chance to bind the returned port.  We can deal with this
      issue if/when we come across it.
      """
  
      tempsock = socket.socket(family, socktype)
      port = bind_port(tempsock)
      tempsock.close()
      del tempsock
      return port
  
  def bind_port(sock, host=HOST):
      """Bind the socket to a free port and return the port number.  Relies on
      ephemeral ports in order to ensure we are using an unbound port.  This is
      important as many tests may be running simultaneously, especially in a
      buildbot environment.  This method raises an exception if the sock.family
      is AF_INET and sock.type is SOCK_STREAM, *and* the socket has SO_REUSEADDR
      or SO_REUSEPORT set on it.  Tests should *never* set these socket options
      for TCP/IP sockets.  The only case for setting these options is testing
      multicasting via multiple UDP sockets.
  
      Additionally, if the SO_EXCLUSIVEADDRUSE socket option is available (i.e.
      on Windows), it will be set on the socket.  This will prevent anyone else
      from bind()'ing to our host/port for the duration of the test.
      """
  
      if sock.family == socket.AF_INET and sock.type == socket.SOCK_STREAM:
          if hasattr(socket, 'SO_REUSEADDR'):
              if sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR) == 1:
                  raise TestFailed("tests should never set the SO_REUSEADDR "   \
                                   "socket option on TCP/IP sockets!")
          if hasattr(socket, 'SO_REUSEPORT'):
              try:
                  if sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT) == 1:
                      raise TestFailed("tests should never set the SO_REUSEPORT "   \
                                       "socket option on TCP/IP sockets!")
              except OSError:
                  # Python's socket module was compiled using modern headers
                  # thus defining SO_REUSEPORT but this process is running
                  # under an older kernel that does not support SO_REUSEPORT.
                  pass
          if hasattr(socket, 'SO_EXCLUSIVEADDRUSE'):
              sock.setsockopt(socket.SOL_SOCKET, socket.SO_EXCLUSIVEADDRUSE, 1)
  
      sock.bind((host, 0))
      port = sock.getsockname()[1]
      return port
  
  def bind_unix_socket(sock, addr):
      """Bind a unix socket, raising SkipTest if PermissionError is raised."""
      assert sock.family == socket.AF_UNIX
      try:
          sock.bind(addr)
      except PermissionError:
          sock.close()
          raise unittest.SkipTest('cannot bind AF_UNIX sockets')
  
  def _is_ipv6_enabled():
      """Check whether IPv6 is enabled on this host."""
      if socket.has_ipv6:
          sock = None
          try:
              sock = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
              sock.bind((HOSTv6, 0))
              return True
          except OSError:
              pass
          finally:
              if sock:
                  sock.close()
      return False
  
  IPV6_ENABLED = _is_ipv6_enabled()
  
  def system_must_validate_cert(f):
      """Skip the test on TLS certificate validation failures."""
      @functools.wraps(f)
      def dec(*args, **kwargs):
          try:
              f(*args, **kwargs)
          except IOError as e:
              if "CERTIFICATE_VERIFY_FAILED" in str(e):
                  raise unittest.SkipTest("system does not contain "
                                          "necessary certificates")
              raise
      return dec
  
  # A constant likely larger than the underlying OS pipe buffer size, to
  # make writes blocking.
  # Windows limit seems to be around 512 B, and many Unix kernels have a
  # 64 KiB pipe buffer size or 16 * PAGE_SIZE: take a few megs to be sure.
  # (see issue #17835 for a discussion of this number).
  PIPE_MAX_SIZE = 4 * 1024 * 1024 + 1
  
  # A constant likely larger than the underlying OS socket buffer size, to make
  # writes blocking.
  # The socket buffer sizes can usually be tuned system-wide (e.g. through sysctl
  # on Linux), or on a per-socket basis (SO_SNDBUF/SO_RCVBUF). See issue #18643
  # for a discussion of this number).
  SOCK_MAX_SIZE = 16 * 1024 * 1024 + 1
  
  # decorator for skipping tests on non-IEEE 754 platforms
  requires_IEEE_754 = unittest.skipUnless(
      float.__getformat__("double").startswith("IEEE"),
      "test requires IEEE 754 doubles")
  
  requires_zlib = unittest.skipUnless(zlib, 'requires zlib')
  
  requires_gzip = unittest.skipUnless(gzip, 'requires gzip')
  
  requires_bz2 = unittest.skipUnless(bz2, 'requires bz2')
  
  requires_lzma = unittest.skipUnless(lzma, 'requires lzma')
  
  is_jython = sys.platform.startswith('java')
  
  # TODO: reenable me once sysconfig is properly implemented (GR-9150)
  # _ANDROID_API_LEVEL = sysconfig.get_config_var('ANDROID_API_LEVEL')
  # is_android = (_ANDROID_API_LEVEL is not None and _ANDROID_API_LEVEL > 0)
  is_android = False
  
  if sys.platform != 'win32':
      unix_shell = '/system/bin/sh' if is_android else '/bin/sh'
  else:
      unix_shell = None
  
  # Filename used for testing
  if os.name == 'java':
      # Jython disallows @ in module names
      TESTFN = '$test'
  else:
      TESTFN = '@test'
  
  # Disambiguate TESTFN for parallel testing, while letting it remain a valid
  # module name.
  TESTFN = "{}_{}_tmp".format(TESTFN, os.getpid())
  
  # FS_NONASCII: non-ASCII character encodable by os.fsencode(),
  # or None if there is no such character.
  FS_NONASCII = None
  for character in (
      # First try printable and common characters to have a readable filename.
      # For each character, the encoding list are just example of encodings able
      # to encode the character (the list is not exhaustive).
  
      # U+00E6 (Latin Small Letter Ae): cp1252, iso-8859-1
      '\u00E6',
      # U+0130 (Latin Capital Letter I With Dot Above): cp1254, iso8859_3
      '\u0130',
      # U+0141 (Latin Capital Letter L With Stroke): cp1250, cp1257
      '\u0141',
      # U+03C6 (Greek Small Letter Phi): cp1253
      '\u03C6',
      # U+041A (Cyrillic Capital Letter Ka): cp1251
      '\u041A',
      # U+05D0 (Hebrew Letter Alef): Encodable to cp424
      '\u05D0',
      # U+060C (Arabic Comma): cp864, cp1006, iso8859_6, mac_arabic
      '\u060C',
      # U+062A (Arabic Letter Teh): cp720
      '\u062A',
      # U+0E01 (Thai Character Ko Kai): cp874
      '\u0E01',
  
      # Then try more "special" characters. "special" because they may be
      # interpreted or displayed differently depending on the exact locale
      # encoding and the font.
  
      # U+00A0 (No-Break Space)
      '\u00A0',
      # U+20AC (Euro Sign)
      '\u20AC',
  ):
      try:
          os.fsdecode(os.fsencode(character))
      except UnicodeError:
          pass
      else:
          FS_NONASCII = character
          break
  
  # TESTFN_UNICODE is a non-ascii filename
  TESTFN_UNICODE = TESTFN + "-\xe0\xf2\u0258\u0141\u011f"
  if sys.platform == 'darwin':
      # In Mac OS X's VFS API file names are, by definition, canonically
      # decomposed Unicode, encoded using UTF-8. See QA1173:
      # http://developer.apple.com/mac/library/qa/qa2001/qa1173.html
      import unicodedata
      TESTFN_UNICODE = unicodedata.normalize('NFD', TESTFN_UNICODE)
  TESTFN_ENCODING = sys.getfilesystemencoding()
  
  # TESTFN_UNENCODABLE is a filename (str type) that should *not* be able to be
  # encoded by the filesystem encoding (in strict mode). It can be None if we
  # cannot generate such filename.
  TESTFN_UNENCODABLE = None
  if os.name == 'nt':
      # skip win32s (0) or Windows 9x/ME (1)
      if sys.getwindowsversion().platform >= 2:
          # Different kinds of characters from various languages to minimize the
          # probability that the whole name is encodable to MBCS (issue #9819)
          TESTFN_UNENCODABLE = TESTFN + "-\u5171\u0141\u2661\u0363\uDC80"
          try:
              TESTFN_UNENCODABLE.encode(TESTFN_ENCODING)
          except UnicodeEncodeError:
              pass
          else:
              print('WARNING: The filename %r CAN be encoded by the filesystem encoding (%s). '
                    'Unicode filename tests may not be effective'
                    % (TESTFN_UNENCODABLE, TESTFN_ENCODING))
              TESTFN_UNENCODABLE = None
  # Mac OS X denies unencodable filenames (invalid utf-8)
  elif sys.platform != 'darwin':
      try:
          # ascii and utf-8 cannot encode the byte 0xff
          b'\xff'.decode(TESTFN_ENCODING)
      except UnicodeDecodeError:
          # 0xff will be encoded using the surrogate character u+DCFF
          TESTFN_UNENCODABLE = TESTFN \
              + b'-\xff'.decode(TESTFN_ENCODING, 'surrogateescape')
      else:
          # File system encoding (eg. ISO-8859-* encodings) can encode
          # the byte 0xff. Skip some unicode filename tests.
          pass
  
  # TESTFN_UNDECODABLE is a filename (bytes type) that should *not* be able to be
  # decoded from the filesystem encoding (in strict mode). It can be None if we
  # cannot generate such filename (ex: the latin1 encoding can decode any byte
  # sequence). On UNIX, TESTFN_UNDECODABLE can be decoded by os.fsdecode() thanks
  # to the surrogateescape error handler (PEP 383), but not from the filesystem
  # encoding in strict mode.
  TESTFN_UNDECODABLE = None
  for name in (
      # b'\xff' is not decodable by os.fsdecode() with code page 932. Windows
      # accepts it to create a file or a directory, or don't accept to enter to
      # such directory (when the bytes name is used). So test b'\xe7' first: it is
      # not decodable from cp932.
      b'\xe7w\xf0',
      # undecodable from ASCII, UTF-8
      b'\xff',
      # undecodable from iso8859-3, iso8859-6, iso8859-7, cp424, iso8859-8, cp856
      # and cp857
      b'\xae\xd5'
      # undecodable from UTF-8 (UNIX and Mac OS X)
      b'\xed\xb2\x80', b'\xed\xb4\x80',
      # undecodable from shift_jis, cp869, cp874, cp932, cp1250, cp1251, cp1252,
      # cp1253, cp1254, cp1255, cp1257, cp1258
      b'\x81\x98',
  ):
      try:
          name.decode(TESTFN_ENCODING)
      except UnicodeDecodeError:
          TESTFN_UNDECODABLE = os.fsencode(TESTFN) + name
          break
  
  if FS_NONASCII:
      TESTFN_NONASCII = TESTFN + '-' + FS_NONASCII
  else:
      TESTFN_NONASCII = None
  
  # Save the initial cwd
  SAVEDCWD = os.getcwd()
  
  # Set by libregrtest/main.py so we can skip tests that are not
  # useful for PGO
  PGO = False
  
  @contextlib.contextmanager
  def temp_dir(path=None, quiet=False):
      """Return a context manager that creates a temporary directory.
  
      Arguments:
  
        path: the directory to create temporarily.  If omitted or None,
          defaults to creating a temporary directory using tempfile.mkdtemp.
  
        quiet: if False (the default), the context manager raises an exception
          on error.  Otherwise, if the path is specified and cannot be
          created, only a warning is issued.
  
      """
      dir_created = False
      if path is None:
          path = tempfile.mkdtemp()
          dir_created = True
          path = os.path.realpath(path)
      else:
          try:
              os.mkdir(path)
              dir_created = True
          except OSError:
              if not quiet:
                  raise
              warnings.warn('tests may fail, unable to create temp dir: ' + path,
                            RuntimeWarning, stacklevel=3)
      if dir_created:
          pid = os.getpid()
      try:
          yield path
      finally:
          # In case the process forks, let only the parent remove the
          # directory. The child has a diffent process id. (bpo-30028)
          if dir_created and pid == os.getpid():
              rmtree(path)
  
  @contextlib.contextmanager
  def change_cwd(path, quiet=False):
      """Return a context manager that changes the current working directory.
  
      Arguments:
  
        path: the directory to use as the temporary current working directory.
  
        quiet: if False (the default), the context manager raises an exception
          on error.  Otherwise, it issues only a warning and keeps the current
          working directory the same.
  
      """
      saved_dir = os.getcwd()
      try:
          os.chdir(path)
      except OSError:
          if not quiet:
              raise
          warnings.warn('tests may fail, unable to change CWD to: ' + path,
                        RuntimeWarning, stacklevel=3)
      try:
          yield os.getcwd()
      finally:
          os.chdir(saved_dir)
  
  
  @contextlib.contextmanager
  def temp_cwd(name='tempcwd', quiet=False):
      """
      Context manager that temporarily creates and changes the CWD.
  
      The function temporarily changes the current working directory
      after creating a temporary directory in the current directory with
      name *name*.  If *name* is None, the temporary directory is
      created using tempfile.mkdtemp.
  
      If *quiet* is False (default) and it is not possible to
      create or change the CWD, an error is raised.  If *quiet* is True,
      only a warning is raised and the original CWD is used.
  
      """
      with temp_dir(path=name, quiet=quiet) as temp_path:
          with change_cwd(temp_path, quiet=quiet) as cwd_dir:
              yield cwd_dir
  
  if hasattr(os, "umask"):
      @contextlib.contextmanager
      def temp_umask(umask):
          """Context manager that temporarily sets the process umask."""
          oldmask = os.umask(umask)
          try:
              yield
          finally:
              os.umask(oldmask)
  
  # TEST_HOME_DIR refers to the top level directory of the "test" package
  # that contains Python's regression test suite
  TEST_SUPPORT_DIR = os.path.dirname(os.path.abspath(__file__))
  TEST_HOME_DIR = os.path.dirname(TEST_SUPPORT_DIR)
  
  # TEST_DATA_DIR is used as a target download location for remote resources
  TEST_DATA_DIR = os.path.join(TEST_HOME_DIR, "data")
  
  def findfile(filename, subdir=None):
      """Try to find a file on sys.path or in the test directory.  If it is not
      found the argument passed to the function is returned (this does not
      necessarily signal failure; could still be the legitimate path).
  
      Setting *subdir* indicates a relative path to use to find the file
      rather than looking directly in the path directories.
      """
      if os.path.isabs(filename):
          return filename
      if subdir is not None:
          filename = os.path.join(subdir, filename)
      path = [TEST_HOME_DIR] + sys.path
      for dn in path:
          fn = os.path.join(dn, filename)
          if os.path.exists(fn): return fn
      return filename
  
  def create_empty_file(filename):
      """Create an empty file. If the file already exists, truncate it."""
      fd = os.open(filename, os.O_WRONLY | os.O_CREAT | os.O_TRUNC)
      os.close(fd)
  
  def sortdict(dict):
      "Like repr(dict), but in sorted order."
      items = sorted(dict.items())
      reprpairs = ["%r: %r" % pair for pair in items]
      withcommas = ", ".join(reprpairs)
      return "{%s}" % withcommas
  
  def make_bad_fd():
      """
      Create an invalid file descriptor by opening and closing a file and return
      its fd.
      """
      file = open(TESTFN, "wb")
      try:
          return file.fileno()
      finally:
          file.close()
          unlink(TESTFN)
  
  def check_syntax_error(testcase, statement, *, lineno=None, offset=None):
      with testcase.assertRaises(SyntaxError) as cm:
          compile(statement, '<test string>', 'exec')
      err = cm.exception
      testcase.assertIsNotNone(err.lineno)
      if lineno is not None:
          testcase.assertEqual(err.lineno, lineno)
      testcase.assertIsNotNone(err.offset)
      if offset is not None:
          testcase.assertEqual(err.offset, offset)
  
  def open_urlresource(url, *args, **kw):
      import urllib.request, urllib.parse
  
      check = kw.pop('check', None)
  
      filename = urllib.parse.urlparse(url)[2].split('/')[-1] # '/': it's URL!
  
      fn = os.path.join(TEST_DATA_DIR, filename)
  
      def check_valid_file(fn):
          f = open(fn, *args, **kw)
          if check is None:
              return f
          elif check(f):
              f.seek(0)
              return f
          f.close()
  
      if os.path.exists(fn):
          f = check_valid_file(fn)
          if f is not None:
              return f
          unlink(fn)
  
      # Verify the requirement before downloading the file
      requires('urlfetch')
  
      if verbose:
          print('\tfetching %s ...' % url, file=get_original_stdout())
      opener = urllib.request.build_opener()
      if gzip:
          opener.addheaders.append(('Accept-Encoding', 'gzip'))
      f = opener.open(url, timeout=15)
      if gzip and f.headers.get('Content-Encoding') == 'gzip':
          f = gzip.GzipFile(fileobj=f)
      try:
          with open(fn, "wb") as out:
              s = f.read()
              while s:
                  out.write(s)
                  s = f.read()
      finally:
          f.close()
  
      f = check_valid_file(fn)
      if f is not None:
          return f
      raise TestFailed('invalid resource %r' % fn)
  
  
  class WarningsRecorder(object):
      """Convenience wrapper for the warnings list returned on
         entry to the warnings.catch_warnings() context manager.
      """
      def __init__(self, warnings_list):
          self._warnings = warnings_list
          self._last = 0
  
      def __getattr__(self, attr):
          if len(self._warnings) > self._last:
              return getattr(self._warnings[-1], attr)
          elif attr in warnings.WarningMessage._WARNING_DETAILS:
              return None
          raise AttributeError("%r has no attribute %r" % (self, attr))
  
      @property
      def warnings(self):
          return self._warnings[self._last:]
  
      def reset(self):
          self._last = len(self._warnings)
  
  
  def _filterwarnings(filters, quiet=False):
      """Catch the warnings, then check if all the expected
      warnings have been raised and re-raise unexpected warnings.
      If 'quiet' is True, only re-raise the unexpected warnings.
      """
      # Clear the warning registry of the calling module
      # in order to re-raise the warnings.
      frame = sys._getframe(2)
      registry = frame.f_globals.get('__warningregistry__')
      if registry:
          registry.clear()
      with warnings.catch_warnings(record=True) as w:
          # Set filter "always" to record all warnings.  Because
          # test_warnings swap the module, we need to look up in
          # the sys.modules dictionary.
          sys.modules['warnings'].simplefilter("always")
          yield WarningsRecorder(w)
      # Filter the recorded warnings
      reraise = list(w)
      missing = []
      for msg, cat in filters:
          seen = False
          for w in reraise[:]:
              warning = w.message
              # Filter out the matching messages
              if (re.match(msg, str(warning), re.I) and
                  issubclass(warning.__class__, cat)):
                  seen = True
                  reraise.remove(w)
          if not seen and not quiet:
              # This filter caught nothing
              missing.append((msg, cat.__name__))
      if reraise:
          raise AssertionError("unhandled warning %s" % reraise[0])
      if missing:
          raise AssertionError("filter (%r, %s) did not catch any warning" %
                               missing[0])
  
  
  @contextlib.contextmanager
  def check_warnings(*filters, **kwargs):
      """Context manager to silence warnings.
  
      Accept 2-tuples as positional arguments:
          ("message regexp", WarningCategory)
  
      Optional argument:
       - if 'quiet' is True, it does not fail if a filter catches nothing
          (default True without argument,
           default False if some filters are defined)
  
      Without argument, it defaults to:
          check_warnings(("", Warning), quiet=True)
      """
      quiet = kwargs.get('quiet')
      if not filters:
          filters = (("", Warning),)
          # Preserve backward compatibility
          if quiet is None:
              quiet = True
      return _filterwarnings(filters, quiet)
  
  
  @contextlib.contextmanager
  def check_no_resource_warning(testcase):
      """Context manager to check that no ResourceWarning is emitted.
  
      Usage:
  
          with check_no_resource_warning(self):
              f = open(...)
              ...
              del f
  
      You must remove the object which may emit ResourceWarning before
      the end of the context manager.
      """
      with warnings.catch_warnings(record=True) as warns:
          warnings.filterwarnings('always', category=ResourceWarning)
          yield
          gc_collect()
      testcase.assertEqual(warns, [])
  
  
  class CleanImport(object):
      """Context manager to force import to return a new module reference.
  
      This is useful for testing module-level behaviours, such as
      the emission of a DeprecationWarning on import.
  
      Use like this:
  
          with CleanImport("foo"):
              importlib.import_module("foo") # new reference
      """
  
      def __init__(self, *module_names):
          self.original_modules = sys.modules.copy()
          for module_name in module_names:
              if module_name in sys.modules:
                  module = sys.modules[module_name]
                  # It is possible that module_name is just an alias for
                  # another module (e.g. stub for modules renamed in 3.x).
                  # In that case, we also need delete the real module to clear
                  # the import cache.
                  if module.__name__ != module_name:
                      del sys.modules[module.__name__]
                  del sys.modules[module_name]
  
      def __enter__(self):
          return self
  
      def __exit__(self, *ignore_exc):
          sys.modules.update(self.original_modules)
  
  
  class EnvironmentVarGuard(collections.abc.MutableMapping):
  
      """Class to help protect the environment variable properly.  Can be used as
      a context manager."""
  
      def __init__(self):
          self._environ = os.environ
          self._changed = {}
  
      def __getitem__(self, envvar):
          return self._environ[envvar]
  
      def __setitem__(self, envvar, value):
          # Remember the initial value on the first access
          if envvar not in self._changed:
              self._changed[envvar] = self._environ.get(envvar)
          self._environ[envvar] = value
  
      def __delitem__(self, envvar):
          # Remember the initial value on the first access
          if envvar not in self._changed:
              self._changed[envvar] = self._environ.get(envvar)
          if envvar in self._environ:
              del self._environ[envvar]
  
      def keys(self):
          return self._environ.keys()
  
      def __iter__(self):
          return iter(self._environ)
  
      def __len__(self):
          return len(self._environ)
  
      def set(self, envvar, value):
          self[envvar] = value
  
      def unset(self, envvar):
          del self[envvar]
  
      def __enter__(self):
          return self
  
      def __exit__(self, *ignore_exc):
          for (k, v) in self._changed.items():
              if v is None:
                  if k in self._environ:
                      del self._environ[k]
              else:
                  self._environ[k] = v
          os.environ = self._environ
  
  
  class DirsOnSysPath(object):
      """Context manager to temporarily add directories to sys.path.
  
      This makes a copy of sys.path, appends any directories given
      as positional arguments, then reverts sys.path to the copied
      settings when the context ends.
  
      Note that *all* sys.path modifications in the body of the
      context manager, including replacement of the object,
      will be reverted at the end of the block.
      """
  
      def __init__(self, *paths):
          self.original_value = sys.path[:]
          self.original_object = sys.path
          sys.path.extend(paths)
  
      def __enter__(self):
          return self
  
      def __exit__(self, *ignore_exc):
          sys.path = self.original_object
          sys.path[:] = self.original_value
  
  
  class TransientResource(object):
  
      """Raise ResourceDenied if an exception is raised while the context manager
      is in effect that matches the specified exception and attributes."""
  
      def __init__(self, exc, **kwargs):
          self.exc = exc
          self.attrs = kwargs
  
      def __enter__(self):
          return self
  
      def __exit__(self, type_=None, value=None, traceback=None):
          """If type_ is a subclass of self.exc and value has attributes matching
          self.attrs, raise ResourceDenied.  Otherwise let the exception
          propagate (if any)."""
          if type_ is not None and issubclass(self.exc, type_):
              for attr, attr_value in self.attrs.items():
                  if not hasattr(value, attr):
                      break
                  if getattr(value, attr) != attr_value:
                      break
              else:
                  raise ResourceDenied("an optional resource is not available")
  
  # Context managers that raise ResourceDenied when various issues
  # with the Internet connection manifest themselves as exceptions.
  # XXX deprecate these and use transient_internet() instead
  time_out = TransientResource(OSError, errno=errno.ETIMEDOUT)
  socket_peer_reset = TransientResource(OSError, errno=errno.ECONNRESET)
  ioerror_peer_reset = TransientResource(OSError, errno=errno.ECONNRESET)
  
  
  @contextlib.contextmanager
  def transient_internet(resource_name, *, timeout=30.0, errnos=()):
      """Return a context manager that raises ResourceDenied when various issues
      with the Internet connection manifest themselves as exceptions."""
      default_errnos = [
          ('ECONNREFUSED', 111),
          ('ECONNRESET', 104),
          ('EHOSTUNREACH', 113),
          ('ENETUNREACH', 101),
          ('ETIMEDOUT', 110),
      ]
      default_gai_errnos = [
          ('EAI_AGAIN', -3),
          ('EAI_FAIL', -4),
          ('EAI_NONAME', -2),
          ('EAI_NODATA', -5),
          # Encountered when trying to resolve IPv6-only hostnames
          ('WSANO_DATA', 11004),
      ]
  
      denied = ResourceDenied("Resource %r is not available" % resource_name)
      captured_errnos = errnos
      gai_errnos = []
      if not captured_errnos:
          captured_errnos = [getattr(errno, name, num)
                             for (name, num) in default_errnos]
          gai_errnos = [getattr(socket, name, num)
                        for (name, num) in default_gai_errnos]
  
      def filter_error(err):
          n = getattr(err, 'errno', None)
          if (isinstance(err, socket.timeout) or
              (isinstance(err, socket.gaierror) and n in gai_errnos) or
              (isinstance(err, urllib.error.HTTPError) and
               500 <= err.code <= 599) or
              (isinstance(err, urllib.error.URLError) and
                   (("ConnectionRefusedError" in err.reason) or
                    ("TimeoutError" in err.reason) or
                    ("EOFError" in err.reason))) or
              n in captured_errnos):
              if not verbose:
                  sys.stderr.write(denied.args[0] + "\n")
              raise denied from err
  
      old_timeout = socket.getdefaulttimeout()
      try:
          if timeout is not None:
              socket.setdefaulttimeout(timeout)
          yield
      except nntplib.NNTPTemporaryError as err:
          if verbose:
              sys.stderr.write(denied.args[0] + "\n")
          raise denied from err
      except OSError as err:
          # urllib can wrap original socket errors multiple times (!), we must
          # unwrap to get at the original error.
          while True:
              a = err.args
              if len(a) >= 1 and isinstance(a[0], OSError):
                  err = a[0]
              # The error can also be wrapped as args[1]:
              #    except socket.error as msg:
              #        raise OSError('socket error', msg).with_traceback(sys.exc_info()[2])
              elif len(a) >= 2 and isinstance(a[1], OSError):
                  err = a[1]
              else:
                  break
          filter_error(err)
          raise
      # XXX should we catch generic exceptions and look for their
      # __cause__ or __context__?
      finally:
          socket.setdefaulttimeout(old_timeout)
  
  
  @contextlib.contextmanager
  def captured_output(stream_name):
      """Return a context manager used by captured_stdout/stdin/stderr
      that temporarily replaces the sys stream *stream_name* with a StringIO."""
      import io
      orig_stdout = getattr(sys, stream_name)
      setattr(sys, stream_name, io.StringIO())
      try:
          yield getattr(sys, stream_name)
      finally:
          setattr(sys, stream_name, orig_stdout)
  
  def captured_stdout():
      """Capture the output of sys.stdout:
  
         with captured_stdout() as stdout:
             print("hello")
         self.assertEqual(stdout.getvalue(), "hello\\n")
      """
      return captured_output("stdout")
  
  def captured_stderr():
      """Capture the output of sys.stderr:
  
         with captured_stderr() as stderr:
             print("hello", file=sys.stderr)
         self.assertEqual(stderr.getvalue(), "hello\\n")
      """
      return captured_output("stderr")
  
  def captured_stdin():
      """Capture the input to sys.stdin:
  
         with captured_stdin() as stdin:
             stdin.write('hello\\n')
             stdin.seek(0)
             # call test code that consumes from sys.stdin
             captured = input()
         self.assertEqual(captured, "hello")
      """
      return captured_output("stdin")
  
  
  def gc_collect():
      """Force as many objects as possible to be collected.
  
      In non-CPython implementations of Python, this is needed because timely
      deallocation is not guaranteed by the garbage collector.  (Even in CPython
      this can be the case in case of reference cycles.)  This means that __del__
      methods may be called later than expected and weakrefs may remain alive for
      longer than expected.  This function tries its best to force all garbage
      objects to disappear.
      """
      gc.collect()
      if is_jython:
          time.sleep(0.1)
      gc.collect()
      gc.collect()
  
  @contextlib.contextmanager
  def disable_gc():
      have_gc = gc.isenabled()
      gc.disable()
      try:
          yield
      finally:
          if have_gc:
              gc.enable()
  
  
  def python_is_optimized():
      """Find if Python was built with optimizations."""
      cflags = sysconfig.get_config_var('PY_CFLAGS') or ''
      final_opt = ""
      for opt in cflags.split():
          if opt.startswith('-O'):
              final_opt = opt
      return final_opt not in ('', '-O0', '-Og')
  
  
  _header = 'nP'
  _align = '0n'
  if hasattr(sys, "gettotalrefcount"):
      _header = '2P' + _header
      _align = '0P'
  _vheader = _header + 'n'
  
  def calcobjsize(fmt):
      return struct.calcsize(_header + fmt + _align)
  
  def calcvobjsize(fmt):
      return struct.calcsize(_vheader + fmt + _align)
  
  
  _TPFLAGS_HAVE_GC = 1<<14
  _TPFLAGS_HEAPTYPE = 1<<9
  
  def check_sizeof(test, o, size):
      import _testcapi
      result = sys.getsizeof(o)
      # add GC header size
      if ((type(o) == type) and (o.__flags__ & _TPFLAGS_HEAPTYPE) or\
          ((type(o) != type) and (type(o).__flags__ & _TPFLAGS_HAVE_GC))):
          size += _testcapi.SIZEOF_PYGC_HEAD
      msg = 'wrong size for %s: got %d, expected %d' \
              % (type(o), result, size)
      test.assertEqual(result, size, msg)
  
  #=======================================================================
  # Decorator for running a function in a different locale, correctly resetting
  # it afterwards.
  
  def run_with_locale(catstr, *locales):
      def decorator(func):
          def inner(*args, **kwds):
              try:
                  import locale
                  category = getattr(locale, catstr)
                  orig_locale = locale.setlocale(category)
              except AttributeError:
                  # if the test author gives us an invalid category string
                  raise
              except:
                  # cannot retrieve original locale, so do nothing
                  locale = orig_locale = None
              else:
                  for loc in locales:
                      try:
                          locale.setlocale(category, loc)
                          break
                      except:
                          pass
  
              # now run the function, resetting the locale on exceptions
              try:
                  return func(*args, **kwds)
              finally:
                  if locale and orig_locale:
                      locale.setlocale(category, orig_locale)
          inner.__name__ = func.__name__
          inner.__doc__ = func.__doc__
          return inner
      return decorator
  
  #=======================================================================
  # Decorator for running a function in a specific timezone, correctly
  # resetting it afterwards.
  
  def run_with_tz(tz):
      def decorator(func):
          def inner(*args, **kwds):
              try:
                  tzset = time.tzset
              except AttributeError:
                  raise unittest.SkipTest("tzset required")
              if 'TZ' in os.environ:
                  orig_tz = os.environ['TZ']
              else:
                  orig_tz = None
              os.environ['TZ'] = tz
              tzset()
  
              # now run the function, resetting the tz on exceptions
              try:
                  return func(*args, **kwds)
              finally:
                  if orig_tz is None:
                      del os.environ['TZ']
                  else:
                      os.environ['TZ'] = orig_tz
                  time.tzset()
  
          inner.__name__ = func.__name__
          inner.__doc__ = func.__doc__
          return inner
      return decorator
  
  #=======================================================================
  # Big-memory-test support. Separate from 'resources' because memory use
  # should be configurable.
  
  # Some handy shorthands. Note that these are used for byte-limits as well
  # as size-limits, in the various bigmem tests
  _1M = 1024*1024
  _1G = 1024 * _1M
  _2G = 2 * _1G
  _4G = 4 * _1G
  
  MAX_Py_ssize_t = sys.maxsize
  
  def set_memlimit(limit):
      global max_memuse
      global real_max_memuse
      sizes = {
          'k': 1024,
          'm': _1M,
          'g': _1G,
          't': 1024*_1G,
      }
      m = re.match(r'(\d+(\.\d+)?) (K|M|G|T)b?$', limit,
                   re.IGNORECASE | re.VERBOSE)
      if m is None:
          raise ValueError('Invalid memory limit %r' % (limit,))
      memlimit = int(float(m.group(1)) * sizes[m.group(3).lower()])
      real_max_memuse = memlimit
      if memlimit > MAX_Py_ssize_t:
          memlimit = MAX_Py_ssize_t
      if memlimit < _2G - 1:
          raise ValueError('Memory limit %r too low to be useful' % (limit,))
      max_memuse = memlimit
  
  class _MemoryWatchdog:
      """An object which periodically watches the process' memory consumption
      and prints it out.
      """
  
      def __init__(self):
          self.procfile = '/proc/{pid}/statm'.format(pid=os.getpid())
          self.started = False
  
      def start(self):
          try:
              f = open(self.procfile, 'r')
          except OSError as e:
              warnings.warn('/proc not available for stats: {}'.format(e),
                            RuntimeWarning)
              sys.stderr.flush()
              return
  
          watchdog_script = findfile("memory_watchdog.py")
          self.mem_watchdog = subprocess.Popen([sys.executable, watchdog_script],
                                               stdin=f, stderr=subprocess.DEVNULL)
          f.close()
          self.started = True
  
      def stop(self):
          if self.started:
              self.mem_watchdog.terminate()
              self.mem_watchdog.wait()
  
  
  def bigmemtest(size, memuse, dry_run=True):
      """Decorator for bigmem tests.
  
      'size' is a requested size for the test (in arbitrary, test-interpreted
      units.) 'memuse' is the number of bytes per unit for the test, or a good
      estimate of it. For example, a test that needs two byte buffers, of 4 GiB
      each, could be decorated with @bigmemtest(size=_4G, memuse=2).
  
      The 'size' argument is normally passed to the decorated test method as an
      extra argument. If 'dry_run' is true, the value passed to the test method
      may be less than the requested value. If 'dry_run' is false, it means the
      test doesn't support dummy runs when -M is not specified.
      """
      def decorator(f):
          def wrapper(self):
              size = wrapper.size
              memuse = wrapper.memuse
              if not real_max_memuse:
                  maxsize = 5147
              else:
                  maxsize = size
  
              if ((real_max_memuse or not dry_run)
                  and real_max_memuse < maxsize * memuse):
                  raise unittest.SkipTest(
                      "not enough memory: %.1fG minimum needed"
                      % (size * memuse / (1024 ** 3)))
  
              if real_max_memuse and verbose:
                  print()
                  print(" ... expected peak memory use: {peak:.1f}G"
                        .format(peak=size * memuse / (1024 ** 3)))
                  watchdog = _MemoryWatchdog()
                  watchdog.start()
              else:
                  watchdog = None
  
              try:
                  return f(self, maxsize)
              finally:
                  if watchdog:
                      watchdog.stop()
  
          wrapper.size = size
          wrapper.memuse = memuse
          return wrapper
      return decorator
  
  def bigaddrspacetest(f):
      """Decorator for tests that fill the address space."""
      def wrapper(self):
          if max_memuse < MAX_Py_ssize_t:
              if MAX_Py_ssize_t >= 2**63 - 1 and max_memuse >= 2**31:
                  raise unittest.SkipTest(
                      "not enough memory: try a 32-bit build instead")
              else:
                  raise unittest.SkipTest(
                      "not enough memory: %.1fG minimum needed"
                      % (MAX_Py_ssize_t / (1024 ** 3)))
          else:
              return f(self)
      return wrapper
  
  #=======================================================================
  # unittest integration.
  
  class BasicTestRunner:
      def run(self, test):
          result = unittest.TestResult()
          test(result)
          return result
  
  def _id(obj):
      return obj
  
  def requires_resource(resource):
      if resource == 'gui' and not _is_gui_available():
          return unittest.skip(_is_gui_available.reason)
      if is_resource_enabled(resource):
          return _id
      else:
          return unittest.skip("resource {0!r} is not enabled".format(resource))
  
  def requires_android_level(level, reason):
      if is_android and _ANDROID_API_LEVEL < level:
          return unittest.skip('%s at Android API level %d' %
                               (reason, _ANDROID_API_LEVEL))
      else:
          return _id
  
  def cpython_only(test):
      """
      Decorator for tests only applicable on CPython.
      """
      return impl_detail(cpython=True)(test)
  
  def impl_detail(msg=None, **guards):
      if check_impl_detail(**guards):
          return _id
      if msg is None:
          guardnames, default = _parse_guards(guards)
          if default:
              msg = "implementation detail not available on {0}"
          else:
              msg = "implementation detail specific to {0}"
          guardnames = sorted(guardnames.keys())
          msg = msg.format(' or '.join(guardnames))
      return unittest.skip(msg)
  
  _have_mp_queue = None
  def requires_multiprocessing_queue(test):
      """Skip decorator for tests that use multiprocessing.Queue."""
      global _have_mp_queue
      if _have_mp_queue is None:
          import multiprocessing
          # Without a functioning shared semaphore implementation attempts to
          # instantiate a Queue will result in an ImportError (issue #3770).
          try:
              multiprocessing.Queue()
              _have_mp_queue = True
          except ImportError:
              _have_mp_queue = False
      msg = "requires a functioning shared semaphore implementation"
      return test if _have_mp_queue else unittest.skip(msg)(test)
  
  def _parse_guards(guards):
      # Returns a tuple ({platform_name: run_me}, default_value)
      if not guards:
          return ({'cpython': True}, False)
      is_true = list(guards.values())[0]
      assert list(guards.values()) == [is_true] * len(guards)   # all True or all False
      return (guards, not is_true)
  
  # Use the following check to guard CPython's implementation-specific tests --
  # or to run them only on the implementation(s) guarded by the arguments.
  def check_impl_detail(**guards):
      """This function returns True or False depending on the host platform.
         Examples:
            if check_impl_detail():               # only on CPython (default)
            if check_impl_detail(jython=True):    # only on Jython
            if check_impl_detail(cpython=False):  # everywhere except on CPython
      """
      guards, default = _parse_guards(guards)
      return guards.get(platform.python_implementation().lower(), default)
  
  
  def no_tracing(func):
      """Decorator to temporarily turn off tracing for the duration of a test."""
      if not hasattr(sys, 'gettrace'):
          return func
      else:
          @functools.wraps(func)
          def wrapper(*args, **kwargs):
              original_trace = sys.gettrace()
              try:
                  sys.settrace(None)
                  return func(*args, **kwargs)
              finally:
                  sys.settrace(original_trace)
          return wrapper
  
  
  def refcount_test(test):
      """Decorator for tests which involve reference counting.
  
      To start, the decorator does not run the test if is not run by CPython.
      After that, any trace function is unset during the test to prevent
      unexpected refcounts caused by the trace function.
  
      """
      return no_tracing(cpython_only(test))
  
  
  def _filter_suite(suite, pred):
      """Recursively filter test cases in a suite based on a predicate."""
      newtests = []
      for test in suite._tests:
          if isinstance(test, unittest.TestSuite):
              _filter_suite(test, pred)
              newtests.append(test)
          else:
              if pred(test):
                  newtests.append(test)
      suite._tests = newtests
  
  def _run_suite(suite):
      """Run tests from a unittest.TestSuite-derived class."""
      if verbose:
          runner = unittest.TextTestRunner(sys.stdout, verbosity=2,
                                           failfast=failfast)
      else:
          runner = BasicTestRunner()
  
      result = runner.run(suite)
      if not result.wasSuccessful():
          if len(result.errors) == 1 and not result.failures:
              err = result.errors[0][1]
          elif len(result.failures) == 1 and not result.errors:
              err = result.failures[0][1]
          else:
              err = "multiple errors occurred"
              if not verbose: err += "; run in verbose mode for details"
          raise TestFailed(err)
  
  
  # By default, don't filter tests
  _match_test_func = None
  _match_test_patterns = None
  
  
  def match_test(test):
      # Function used by support.run_unittest() and regrtest --list-cases
      if _match_test_func is None:
          return True
      else:
          return _match_test_func(test.id())
  
  
  def _is_full_match_test(pattern):
      # If a pattern contains at least one dot, it's considered
      # as a full test identifier.
      # Example: 'test.test_os.FileTests.test_access'.
      #
      # Reject patterns which contain fnmatch patterns: '*', '?', '[...]'
      # or '[!...]'. For example, reject 'test_access*'.
      return ('.' in pattern) and (not re.search(r'[?*\[\]]', pattern))
  
  
  def set_match_tests(patterns):
      global _match_test_func, _match_test_patterns
  
      if patterns == _match_test_patterns:
          # No change: no need to recompile patterns.
          return
  
      if not patterns:
          func = None
          # set_match_tests(None) behaves as set_match_tests(())
          patterns = ()
      elif all(map(_is_full_match_test, patterns)):
          # Simple case: all patterns are full test identifier.
          # The test.bisect utility only uses such full test identifiers.
          func = set(patterns).__contains__
      else:
          regex = '|'.join(map(fnmatch.translate, patterns))
          # The search *is* case sensitive on purpose:
          # don't use flags=re.IGNORECASE
          regex_match = re.compile(regex).match
  
          def match_test_regex(test_id):
              if regex_match(test_id):
                  # The regex matchs the whole identifier like
                  # 'test.test_os.FileTests.test_access'
                  return True
              else:
                  # Try to match parts of the test identifier.
                  # For example, split 'test.test_os.FileTests.test_access'
                  # into: 'test', 'test_os', 'FileTests' and 'test_access'.
                  return any(map(regex_match, test_id.split(".")))
  
          func = match_test_regex
  
      # Create a copy since patterns can be mutable and so modified later
      _match_test_patterns = tuple(patterns)
      _match_test_func = func
  
  
  
  def run_unittest(*classes):
      """Run tests from unittest.TestCase-derived classes."""
      valid_types = (unittest.TestSuite, unittest.TestCase)
      suite = unittest.TestSuite()
      for cls in classes:
          if isinstance(cls, str):
              if cls in sys.modules:
                  suite.addTest(unittest.findTestCases(sys.modules[cls]))
              else:
                  raise ValueError("str arguments must be keys in sys.modules")
          elif isinstance(cls, valid_types):
              suite.addTest(cls)
          else:
              suite.addTest(unittest.makeSuite(cls))
      _filter_suite(suite, match_test)
      _run_suite(suite)
  
  #=======================================================================
  # Check for the presence of docstrings.
  
  # Rather than trying to enumerate all the cases where docstrings may be
  # disabled, we just check for that directly
  
  def _check_docstrings():
      """Just used to check if docstrings are enabled"""
  
  
  #TODO reenable me once platform and sysconfig are implemented/supported
  # MISSING_C_DOCSTRINGS = (check_impl_detail() and
  #                         sys.platform != 'win32' and
  #                         not sysconfig.get_config_var('WITH_DOC_STRINGS'))
  MISSING_C_DOCSTRINGS = False
  
  HAVE_DOCSTRINGS = (_check_docstrings.__doc__ is not None and
                     not MISSING_C_DOCSTRINGS)
  
  requires_docstrings = unittest.skipUnless(HAVE_DOCSTRINGS,
                                            "test requires docstrings")
  
  
  #=======================================================================
  # doctest driver.
  
  def run_doctest(module, verbosity=None, optionflags=0):
      """Run doctest on the given module.  Return (#failures, #tests).
  
      If optional argument verbosity is not specified (or is None), pass
      support's belief about verbosity on to doctest.  Else doctest's
      usual behavior is used (it searches sys.argv for -v).
      """
  
      import doctest
  
      if verbosity is None:
          verbosity = verbose
      else:
          verbosity = None
  
      f, t = doctest.testmod(module, verbose=verbosity, optionflags=optionflags)
      if f:
          raise TestFailed("%d of %d doctests failed" % (f, t))
      if verbose:
          print('doctest (%s) ... %d tests with zero failures' %
                (module.__name__, t))
      return f, t
  
  
  #=======================================================================
  # Support for saving and restoring the imported modules.
  
  def modules_setup():
      return sys.modules.copy(),
  
  def modules_cleanup(oldmodules):
      # Encoders/decoders are registered permanently within the internal
      # codec cache. If we destroy the corresponding modules their
      # globals will be set to None which will trip up the cached functions.
      encodings = [(k, v) for k, v in sys.modules.items()
                   if k.startswith('encodings.')]
      sys.modules.clear()
      sys.modules.update(encodings)
      # XXX: This kind of problem can affect more than just encodings. In particular
      # extension modules (such as _ssl) don't cope with reloading properly.
      # Really, test modules should be cleaning out the test specific modules they
      # know they added (ala test_runpy) rather than relying on this function (as
      # test_importhooks and test_pkg do currently).
      # Implicitly imported *real* modules should be left alone (see issue 10556).
      sys.modules.update(oldmodules)
  
  #=======================================================================
  # Threading support to prevent reporting refleaks when running regrtest.py -R
  
  # NOTE: we use thread._count() rather than threading.enumerate() (or the
  # moral equivalent thereof) because a threading.Thread object is still alive
  # until its __bootstrap() method has returned, even after it has been
  # unregistered from the threading module.
  # thread._count(), on the other hand, only gets decremented *after* the
  # __bootstrap() method has returned, which gives us reliable reference counts
  # at the end of a test run.
  
  def threading_setup():
      if _thread:
          return _thread._count(), threading._dangling.copy()
      else:
          return 1, ()
  
  def threading_cleanup(*original_values):
      if not _thread:
          return
      _MAX_COUNT = 100
      for count in range(_MAX_COUNT):
          values = _thread._count(), threading._dangling
          if values == original_values:
              break
          time.sleep(0.01)
          gc_collect()
      # XXX print a warning in case of failure?
  
  def reap_threads(func):
      """Use this function when threads are being used.  This will
      ensure that the threads are cleaned up even when the test fails.
      If threading is unavailable this function does nothing.
      """
      if not _thread:
          return func
  
      @functools.wraps(func)
      def decorator(*args):
          key = threading_setup()
          try:
              return func(*args)
          finally:
              threading_cleanup(*key)
      return decorator
  
  def reap_children():
      """Use this function at the end of test_main() whenever sub-processes
      are started.  This will help ensure that no extra children (zombies)
      stick around to hog resources and create problems when looking
      for refleaks.
      """
      # Reap all our dead child processes so we don't leave zombies around.
      # These hog resources and might be causing some of the buildbots to die.
      if hasattr(os, 'waitpid'):
          any_process = -1
          while True:
              try:
                  # This will raise an exception on Windows.  That's ok.
                  pid, status = os.waitpid(any_process, os.WNOHANG)
                  if pid == 0:
                      break
                  print("Warning -- reap_children() reaped child process %s"
                        % pid, file=sys.stderr)
              except:
                  break
  
  @contextlib.contextmanager
  def start_threads(threads, unlock=None):
      threads = list(threads)
      started = []
      try:
          try:
              for t in threads:
                  t.start()
                  started.append(t)
          except:
              if verbose:
                  print("Can't start %d threads, only %d threads started" %
                        (len(threads), len(started)))
              raise
          yield
      finally:
          try:
              if unlock:
                  unlock()
              endtime = starttime = time.time()
              for timeout in range(1, 16):
                  endtime += 60
                  for t in started:
                      t.join(max(endtime - time.time(), 0.01))
                  started = [t for t in started if t.isAlive()]
                  if not started:
                      break
                  if verbose:
                      print('Unable to join %d threads during a period of '
                            '%d minutes' % (len(started), timeout))
          finally:
              started = [t for t in started if t.isAlive()]
              if started:
                  faulthandler.dump_traceback(sys.stdout)
                  raise AssertionError('Unable to join %d threads' % len(started))
  
  @contextlib.contextmanager
  def swap_attr(obj, attr, new_val):
      """Temporary swap out an attribute with a new object.
  
      Usage:
          with swap_attr(obj, "attr", 5):
              ...
  
          This will set obj.attr to 5 for the duration of the with: block,
          restoring the old value at the end of the block. If `attr` doesn't
          exist on `obj`, it will be created and then deleted at the end of the
          block.
  
          The old value (or None if it doesn't exist) will be assigned to the
          target of the "as" clause, if there is one.
      """
      if hasattr(obj, attr):
          real_val = getattr(obj, attr)
          setattr(obj, attr, new_val)
          try:
              yield real_val
          finally:
              setattr(obj, attr, real_val)
      else:
          setattr(obj, attr, new_val)
          try:
              yield
          finally:
              if hasattr(obj, attr):
                  delattr(obj, attr)
  
  @contextlib.contextmanager
  def swap_item(obj, item, new_val):
      """Temporary swap out an item with a new object.
  
      Usage:
          with swap_item(obj, "item", 5):
              ...
  
          This will set obj["item"] to 5 for the duration of the with: block,
          restoring the old value at the end of the block. If `item` doesn't
          exist on `obj`, it will be created and then deleted at the end of the
          block.
  
          The old value (or None if it doesn't exist) will be assigned to the
          target of the "as" clause, if there is one.
      """
      if item in obj:
          real_val = obj[item]
          obj[item] = new_val
          try:
              yield real_val
          finally:
              obj[item] = real_val
      else:
          obj[item] = new_val
          try:
              yield
          finally:
              if item in obj:
                  del obj[item]
  
  def strip_python_stderr(stderr):
      """Strip the stderr of a Python process from potential debug output
      emitted by the interpreter.
  
      This will typically be run on the result of the communicate() method
      of a subprocess.Popen object.
      """
      stderr = re.sub(br"\[\d+ refs, \d+ blocks\]\r?\n?", b"", stderr).strip()
      return stderr
  
  requires_type_collecting = unittest.skipIf(hasattr(sys, 'getcounts'),
                          'types are immortal if COUNT_ALLOCS is defined')
  
  def args_from_interpreter_flags():
      """Return a list of command-line arguments reproducing the current
      settings in sys.flags and sys.warnoptions."""
      return subprocess._args_from_interpreter_flags()
  
  def optim_args_from_interpreter_flags():
      """Return a list of command-line arguments reproducing the current
      optimization settings in sys.flags."""
      return subprocess._optim_args_from_interpreter_flags()
  
  #============================================================
  # Support for assertions about logging.
  #============================================================
  
  class TestHandler(logging.handlers.BufferingHandler):
      def __init__(self, matcher):
          # BufferingHandler takes a "capacity" argument
          # so as to know when to flush. As we're overriding
          # shouldFlush anyway, we can set a capacity of zero.
          # You can call flush() manually to clear out the
          # buffer.
          logging.handlers.BufferingHandler.__init__(self, 0)
          self.matcher = matcher
  
      def shouldFlush(self):
          return False
  
      def emit(self, record):
          self.format(record)
          self.buffer.append(record.__dict__)
  
      def matches(self, **kwargs):
          """
          Look for a saved dict whose keys/values match the supplied arguments.
          """
          result = False
          for d in self.buffer:
              if self.matcher.matches(d, **kwargs):
                  result = True
                  break
          return result
  
  class Matcher(object):
  
      _partial_matches = ('msg', 'message')
  
      def matches(self, d, **kwargs):
          """
          Try to match a single dict with the supplied arguments.
  
          Keys whose values are strings and which are in self._partial_matches
          will be checked for partial (i.e. substring) matches. You can extend
          this scheme to (for example) do regular expression matching, etc.
          """
          result = True
          for k in kwargs:
              v = kwargs[k]
              dv = d.get(k)
              if not self.match_value(k, dv, v):
                  result = False
                  break
          return result
  
      def match_value(self, k, dv, v):
          """
          Try to match a single stored value (dv) with a supplied value (v).
          """
          if type(v) != type(dv):
              result = False
          elif type(dv) is not str or k not in self._partial_matches:
              result = (v == dv)
          else:
              result = dv.find(v) >= 0
          return result
  
  
  _can_symlink = None
  def can_symlink():
      global _can_symlink
      if _can_symlink is not None:
          return _can_symlink
      symlink_path = TESTFN + "can_symlink"
      try:
          os.symlink(TESTFN, symlink_path)
          can = True
      except (OSError, NotImplementedError, AttributeError):
          can = False
      else:
          os.remove(symlink_path)
      _can_symlink = can
      return can
  
  def skip_unless_symlink(test):
      """Skip decorator for tests that require functional symlink"""
      ok = can_symlink()
      msg = "Requires functional symlink implementation"
      return test if ok else unittest.skip(msg)(test)
  
  _can_xattr = None
  def can_xattr():
      global _can_xattr
      if _can_xattr is not None:
          return _can_xattr
      if not hasattr(os, "setxattr"):
          can = False
      else:
          tmp_fp, tmp_name = tempfile.mkstemp()
          try:
              with open(TESTFN, "wb") as fp:
                  try:
                      # TESTFN & tempfile may use different file systems with
                      # different capabilities
                      os.setxattr(tmp_fp, b"user.test", b"")
                      os.setxattr(fp.fileno(), b"user.test", b"")
                      # Kernels < 2.6.39 don't respect setxattr flags.
                      kernel_version = platform.release()
                      m = re.match(r"2.6.(\d{1,2})", kernel_version)
                      can = m is None or int(m.group(1)) >= 39
                  except OSError:
                      can = False
          finally:
              unlink(TESTFN)
              unlink(tmp_name)
      _can_xattr = can
      return can
  
  def skip_unless_xattr(test):
      """Skip decorator for tests that require functional extended attributes"""
      ok = can_xattr()
      msg = "no non-broken extended attribute support"
      return test if ok else unittest.skip(msg)(test)
  
  
  def fs_is_case_insensitive(directory):
      """Detects if the file system for the specified directory is case-insensitive."""
      with tempfile.NamedTemporaryFile(dir=directory) as base:
          base_path = base.name
          case_path = base_path.upper()
          if case_path == base_path:
              case_path = base_path.lower()
          try:
              return os.path.samefile(base_path, case_path)
          except FileNotFoundError:
              return False
  
  
  def detect_api_mismatch(ref_api, other_api, *, ignore=()):
      """Returns the set of items in ref_api not in other_api, except for a
      defined list of items to be ignored in this check.
  
      By default this skips private attributes beginning with '_' but
      includes all magic methods, i.e. those starting and ending in '__'.
      """
      missing_items = set(dir(ref_api)) - set(dir(other_api))
      if ignore:
          missing_items -= set(ignore)
      missing_items = set(m for m in missing_items
                          if not m.startswith('_') or m.endswith('__'))
      return missing_items
  
  
  def check__all__(test_case, module, name_of_module=None, extra=(),
                   blacklist=()):
      """Assert that the __all__ variable of 'module' contains all public names.
  
      The module's public names (its API) are detected automatically based on
      whether they match the public name convention and were defined in
      'module'.
  
      The 'name_of_module' argument can specify (as a string or tuple thereof)
      what module(s) an API could be defined in in order to be detected as a
      public API. One case for this is when 'module' imports part of its public
      API from other modules, possibly a C backend (like 'csv' and its '_csv').
  
      The 'extra' argument can be a set of names that wouldn't otherwise be
      automatically detected as "public", like objects without a proper
      '__module__' attriubute. If provided, it will be added to the
      automatically detected ones.
  
      The 'blacklist' argument can be a set of names that must not be treated
      as part of the public API even though their names indicate otherwise.
  
      Usage:
          import bar
          import foo
          import unittest
          from test import support
  
          class MiscTestCase(unittest.TestCase):
              def test__all__(self):
                  support.check__all__(self, foo)
  
          class OtherTestCase(unittest.TestCase):
              def test__all__(self):
                  extra = {'BAR_CONST', 'FOO_CONST'}
                  blacklist = {'baz'}  # Undocumented name.
                  # bar imports part of its API from _bar.
                  support.check__all__(self, bar, ('bar', '_bar'),
                                       extra=extra, blacklist=blacklist)
  
      """
  
      if name_of_module is None:
          name_of_module = (module.__name__, )
      elif isinstance(name_of_module, str):
          name_of_module = (name_of_module, )
  
      expected = set(extra)
  
      for name in dir(module):
          if name.startswith('_') or name in blacklist:
              continue
          obj = getattr(module, name)
          if (getattr(obj, '__module__', None) in name_of_module or
                  (not hasattr(obj, '__module__') and
                   not isinstance(obj, types.ModuleType))):
              expected.add(name)
      test_case.assertCountEqual(module.__all__, expected)
  
  
  class SuppressCrashReport:
      """Try to prevent a crash report from popping up.
  
      On Windows, don't display the Windows Error Reporting dialog.  On UNIX,
      disable the creation of coredump file.
      """
      old_value = None
      old_modes = None
  
      def __enter__(self):
          """On Windows, disable Windows Error Reporting dialogs using
          SetErrorMode.
  
          On UNIX, try to save the previous core file size limit, then set
          soft limit to 0.
          """
          if sys.platform.startswith('win'):
              # see http://msdn.microsoft.com/en-us/library/windows/desktop/ms680621.aspx
              # GetErrorMode is not available on Windows XP and Windows Server 2003,
              # but SetErrorMode returns the previous value, so we can use that
              import ctypes
              self._k32 = ctypes.windll.kernel32
              SEM_NOGPFAULTERRORBOX = 0x02
              self.old_value = self._k32.SetErrorMode(SEM_NOGPFAULTERRORBOX)
              self._k32.SetErrorMode(self.old_value | SEM_NOGPFAULTERRORBOX)
  
              # Suppress assert dialogs in debug builds
              # (see http://bugs.python.org/issue23314)
              try:
                  import msvcrt
                  msvcrt.CrtSetReportMode
              except (AttributeError, ImportError):
                  # no msvcrt or a release build
                  pass
              else:
                  self.old_modes = {}
                  for report_type in [msvcrt.CRT_WARN,
                                      msvcrt.CRT_ERROR,
                                      msvcrt.CRT_ASSERT]:
                      old_mode = msvcrt.CrtSetReportMode(report_type,
                              msvcrt.CRTDBG_MODE_FILE)
                      old_file = msvcrt.CrtSetReportFile(report_type,
                              msvcrt.CRTDBG_FILE_STDERR)
                      self.old_modes[report_type] = old_mode, old_file
  
          else:
              if resource is not None:
                  try:
                      self.old_value = resource.getrlimit(resource.RLIMIT_CORE)
                      resource.setrlimit(resource.RLIMIT_CORE,
                                         (0, self.old_value[1]))
                  except (ValueError, OSError):
                      pass
  
              if sys.platform == 'darwin':
                  # Check if the 'Crash Reporter' on OSX was configured
                  # in 'Developer' mode and warn that it will get triggered
                  # when it is.
                  #
                  # This assumes that this context manager is used in tests
                  # that might trigger the next manager.
                  cmd = ['/usr/bin/defaults', 'read',
                         'com.apple.CrashReporter', 'DialogType']
                  proc = subprocess.Popen(cmd,
                                          stdout=subprocess.PIPE,
                                          stderr=subprocess.PIPE)
                  with proc:
                      stdout = proc.communicate()[0]
                  if stdout.strip() == b'developer':
                      print("this test triggers the Crash Reporter, "
                            "that is intentional", end='', flush=True)
  
          return self
  
      def __exit__(self, *ignore_exc):
          """Restore Windows ErrorMode or core file behavior to initial value."""
          if self.old_value is None:
              return
  
          if sys.platform.startswith('win'):
              self._k32.SetErrorMode(self.old_value)
  
              if self.old_modes:
                  import msvcrt
                  for report_type, (old_mode, old_file) in self.old_modes.items():
                      msvcrt.CrtSetReportMode(report_type, old_mode)
                      msvcrt.CrtSetReportFile(report_type, old_file)
          else:
              if resource is not None:
                  try:
                      resource.setrlimit(resource.RLIMIT_CORE, self.old_value)
                  except (ValueError, OSError):
                      pass
  
  
  def patch(test_instance, object_to_patch, attr_name, new_value):
      """Override 'object_to_patch'.'attr_name' with 'new_value'.
  
      Also, add a cleanup procedure to 'test_instance' to restore
      'object_to_patch' value for 'attr_name'.
      The 'attr_name' should be a valid attribute for 'object_to_patch'.
  
      """
      # check that 'attr_name' is a real attribute for 'object_to_patch'
      # will raise AttributeError if it does not exist
      getattr(object_to_patch, attr_name)
  
      # keep a copy of the old value
      attr_is_local = False
      try:
          old_value = object_to_patch.__dict__[attr_name]
      except (AttributeError, KeyError):
          old_value = getattr(object_to_patch, attr_name, None)
      else:
          attr_is_local = True
  
      # restore the value when the test is done
      def cleanup():
          if attr_is_local:
              setattr(object_to_patch, attr_name, old_value)
          else:
              delattr(object_to_patch, attr_name)
  
      test_instance.addCleanup(cleanup)
  
      # actually override the attribute
      setattr(object_to_patch, attr_name, new_value)
  
  
  def run_in_subinterp(code):
      """
      Run code in a subinterpreter. Raise unittest.SkipTest if the tracemalloc
      module is enabled.
      """
      # Issue #10915, #15751: PyGILState_*() functions don't work with
      # sub-interpreters, the tracemalloc module uses these functions internally
      try:
          import tracemalloc
      except ImportError:
          pass
      else:
          if tracemalloc.is_tracing():
              raise unittest.SkipTest("run_in_subinterp() cannot be used "
                                       "if tracemalloc module is tracing "
                                       "memory allocations")
      import _testcapi
      return _testcapi.run_in_subinterp(code)
  
  
  def check_free_after_iterating(test, iter, cls, args=()):
      class A(cls):
          def __del__(self):
              nonlocal done
              done = True
              try:
                  next(it)
              except StopIteration:
                  pass
  
      done = False
      it = iter(A(*args))
      # Issue 26494: Shouldn't crash
      test.assertRaises(StopIteration, next, it)
      # The sequence should be deallocated just after the end of iterating
      gc_collect()
      test.assertTrue(done)
  
  
  def missing_compiler_executable(cmd_names=[]):
      """Check if the compiler components used to build the interpreter exist.
  
      Check for the existence of the compiler executables whose names are listed
      in 'cmd_names' or all the compiler executables when 'cmd_names' is empty
      and return the first missing executable or None when none is found
      missing.
  
      """
      from distutils import ccompiler, sysconfig, spawn
      compiler = ccompiler.new_compiler()
      sysconfig.customize_compiler(compiler)
      for name in compiler.executables:
          if cmd_names and name not in cmd_names:
              continue
          cmd = getattr(compiler, name)
          if cmd_names:
              assert cmd is not None, \
                      "the '%s' executable is not configured" % name
          elif cmd is None:
              continue
          if spawn.find_executable(cmd[0]) is None:
              return cmd[0]
  
  
  _is_android_emulator = None
  def setswitchinterval(interval):
      # Setting a very low gil interval on the Android emulator causes python
      # to hang (issue #26939).
      minimum_interval = 1e-5
      if is_android and interval < minimum_interval:
          global _is_android_emulator
          if _is_android_emulator is None:
              _is_android_emulator = (subprocess.check_output(
                                 ['getprop', 'ro.kernel.qemu']).strip() == b'1')
          if _is_android_emulator:
              interval = minimum_interval
      return sys.setswitchinterval(interval)
  
  
  @contextlib.contextmanager
  def disable_faulthandler():
      # use sys.__stderr__ instead of sys.stderr, since regrtest replaces
      # sys.stderr with a StringIO which has no file descriptor when a test
      # is run with -W/--verbose3.
      fd = sys.__stderr__.fileno()
  
      is_enabled = faulthandler.is_enabled()
      try:
          faulthandler.disable()
          yield
      finally:
          if is_enabled:
              faulthandler.enable(file=fd, all_threads=True)
  
  
  class SaveSignals:
      """
      Save an restore signal handlers.
  
      This class is only able to save/restore signal handlers registered
      by the Python signal module: see bpo-13285 for "external" signal
      handlers.
      """
  
      def __init__(self):
          import signal
          self.signal = signal
          self.signals = list(range(1, signal.NSIG))
          # SIGKILL and SIGSTOP signals cannot be ignored nor catched
          for signame in ('SIGKILL', 'SIGSTOP'):
              try:
                  signum = getattr(signal, signame)
              except AttributeError:
                  continue
              self.signals.remove(signum)
          self.handlers = {}
  
      def save(self):
          for signum in self.signals:
              handler = self.signal.getsignal(signum)
              if handler is None:
                  # getsignal() returns None if a signal handler was not
                  # registered by the Python signal module,
                  # and the handler is not SIG_DFL nor SIG_IGN.
                  #
                  # Ignore the signal: we cannot restore the handler.
                  continue
              self.handlers[signum] = handler
  
      def restore(self):
          for signum, handler in self.handlers.items():
              self.signal.signal(signum, handler)
  
  
  class FakePath:
      """Simple implementing of the path protocol.
      """
      def __init__(self, path):
          self.path = path
  
      def __repr__(self):
          return f'<FakePath {self.path!r}>'
  
      def __fspath__(self):
          if (isinstance(self.path, BaseException) or
              isinstance(self.path, type) and
                  issubclass(self.path, BaseException)):
              raise self.path
          else:
              return self.path
  