text: from __future__ import generators
  """
  httplib2
  
  A caching http interface that supports ETags and gzip
  to conserve bandwidth.
  
  Requires Python 2.3 or later
  
  Changelog:
  2007-08-18, Rick: Modified so it's able to use a socks proxy if needed.
  
  """
  
  __author__ = "Joe Gregorio (joe@bitworking.org)"
  __copyright__ = "Copyright 2006, Joe Gregorio"
  __contributors__ = ["Thomas Broyer (t.broyer@ltgt.net)",
      "James Antill",
      "Xavier Verges Farrero",
      "Jonathan Feinberg",
      "Blair Zajac",
      "Sam Ruby",
      "Louis Nyffenegger"]
  __license__ = "MIT"
  __version__ = "0.7.2"
  
  import re
  import sys
  import email
  import email.Utils
  import email.Message
  import email.FeedParser
  import StringIO
  import gzip
  import zlib
  import httplib
  try:
      import urllib.parse as urlparse
  except ImportError:
      import urlparse
  import base64
  import os
  import copy
  import calendar
  import time
  import random
  import errno
  # remove depracated warning in python2.6
  try:
      from hashlib import sha1 as _sha, md5 as _md5
  except ImportError:
      import sha
      import md5
      _sha = sha.new
      _md5 = md5.new
  import hmac
  from gettext import gettext as _
  import socket
  
  try:
      from httplib2 import socks
  except ImportError:
      socks = None
  
  # Build the appropriate socket wrapper for ssl
  try:
      import ssl # python 2.6
      ssl_SSLError = ssl.SSLError
      def _ssl_wrap_socket(sock, key_file, cert_file,
                           disable_validation, ca_certs):
          if disable_validation:
              cert_reqs = ssl.CERT_NONE
          else:
              cert_reqs = ssl.CERT_REQUIRED
          # We should be specifying SSL version 3 or TLS v1, but the ssl module
          # doesn't expose the necessary knobs. So we need to go with the default
          # of SSLv23.
          return ssl.wrap_socket(sock, keyfile=key_file, certfile=cert_file,
                                 cert_reqs=cert_reqs, ca_certs=ca_certs)
  except (AttributeError, ImportError):
      ssl_SSLError = None
      def _ssl_wrap_socket(sock, key_file, cert_file,
                           disable_validation, ca_certs):
          if not disable_validation:
              raise CertificateValidationUnsupported(
                      "SSL certificate validation is not supported without "
                      "the ssl module installed. To avoid this error, install "
                      "the ssl module, or explicity disable validation.")
          ssl_sock = socket.ssl(sock, key_file, cert_file)
          return httplib.FakeSocket(sock, ssl_sock)
  
  
  if sys.version_info >= (2,3):
      from iri2uri import iri2uri
  else:
      def iri2uri(uri):
          return uri
  
  def has_timeout(timeout): # python 2.6
      if hasattr(socket, '_GLOBAL_DEFAULT_TIMEOUT'):
          return (timeout is not None and timeout is not socket._GLOBAL_DEFAULT_TIMEOUT)
      return (timeout is not None)
  
  __all__ = ['Http', 'Response', 'ProxyInfo', 'HttpLib2Error',
    'RedirectMissingLocation', 'RedirectLimit', 'FailedToDecompressContent',
    'UnimplementedDigestAuthOptionError', 'UnimplementedHmacDigestAuthOptionError',
    'debuglevel', 'ProxiesUnavailableError']
  
  
  # The httplib debug level, set to a non-zero value to get debug output
  debuglevel = 0
  
  
  # Python 2.3 support
  if sys.version_info < (2,4):
      def sorted(seq):
          seq.sort()
          return seq
  
  # Python 2.3 support
  def HTTPResponse__getheaders(self):
      """Return list of (header, value) tuples."""
      if self.msg is None:
          raise httplib.ResponseNotReady()
      return self.msg.items()
  
  if not hasattr(httplib.HTTPResponse, 'getheaders'):
      httplib.HTTPResponse.getheaders = HTTPResponse__getheaders
  
  # All exceptions raised here derive from HttpLib2Error
  class HttpLib2Error(Exception): pass
  
  # Some exceptions can be caught and optionally
  # be turned back into responses.
  class HttpLib2ErrorWithResponse(HttpLib2Error):
      def __init__(self, desc, response, content):
          self.response = response
          self.content = content
          HttpLib2Error.__init__(self, desc)
  
  class RedirectMissingLocation(HttpLib2ErrorWithResponse): pass
  class RedirectLimit(HttpLib2ErrorWithResponse): pass
  class FailedToDecompressContent(HttpLib2ErrorWithResponse): pass
  class UnimplementedDigestAuthOptionError(HttpLib2ErrorWithResponse): pass
  class UnimplementedHmacDigestAuthOptionError(HttpLib2ErrorWithResponse): pass
  
  class MalformedHeader(HttpLib2Error): pass
  class RelativeURIError(HttpLib2Error): pass
  class ServerNotFoundError(HttpLib2Error): pass
  class ProxiesUnavailableError(HttpLib2Error): pass
  class CertificateValidationUnsupported(HttpLib2Error): pass
  class SSLHandshakeError(HttpLib2Error): pass
  class NotSupportedOnThisPlatform(HttpLib2Error): pass
  class CertificateHostnameMismatch(SSLHandshakeError):
    def __init__(self, desc, host, cert):
      HttpLib2Error.__init__(self, desc)
      self.host = host
      self.cert = cert
  
  # Open Items:
  # -----------
  # Proxy support
  
  # Are we removing the cached content too soon on PUT (only delete on 200 Maybe?)
  
  # Pluggable cache storage (supports storing the cache in
  #   flat files by default. We need a plug-in architecture
  #   that can support Berkeley DB and Squid)
  
  # == Known Issues ==
  # Does not handle a resource that uses conneg and Last-Modified but no ETag as a cache validator.
  # Does not handle Cache-Control: max-stale
  # Does not use Age: headers when calculating cache freshness.
  
  
  # The number of redirections to follow before giving up.
  # Note that only GET redirects are automatically followed.
  # Will also honor 301 requests by saving that info and never
  # requesting that URI again.
  DEFAULT_MAX_REDIRECTS = 5
  
  # Use system CA certificates
  CA_CERTS = "/etc/ssl/certs/ca-certificates.crt"
  
  # Which headers are hop-by-hop headers by default
  HOP_BY_HOP = ['connection', 'keep-alive', 'proxy-authenticate', 'proxy-authorization', 'te', 'trailers', 'transfer-encoding', 'upgrade']
  
  def _get_end2end_headers(response):
      hopbyhop = list(HOP_BY_HOP)
      hopbyhop.extend([x.strip() for x in response.get('connection', '').split(',')])
      return [header for header in response.keys() if header not in hopbyhop]
  
  URI = re.compile(r"^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?")
  
  def parse_uri(uri):
      """Parses a URI using the regex given in Appendix B of RFC 3986.
  
          (scheme, authority, path, query, fragment) = parse_uri(uri)
      """
      groups = URI.match(uri).groups()
      return (groups[1], groups[3], groups[4], groups[6], groups[8])
  
  def urlnorm(uri):
      (scheme, authority, path, query, fragment) = parse_uri(uri)
      if not scheme or not authority:
          raise RelativeURIError("Only absolute URIs are allowed. uri = %s" % uri)
      authority = authority.lower()
      scheme = scheme.lower()
      if not path:
          path = "/"
      # Could do syntax based normalization of the URI before
      # computing the digest. See Section 6.2.2 of Std 66.
      request_uri = query and "?".join([path, query]) or path
      scheme = scheme.lower()
      defrag_uri = scheme + "://" + authority + request_uri
      return scheme, authority, request_uri, defrag_uri
  
  
  # Cache filename construction (original borrowed from Venus http://intertwingly.net/code/venus/)
  re_url_scheme    = re.compile(r'^\w+://')
  re_slash         = re.compile(r'[?/:|]+')
  
  def safename(filename):
      """Return a filename suitable for the cache.
  
      Strips dangerous and common characters to create a filename we
      can use to store the cache in.
      """
  
      try:
          if re_url_scheme.match(filename):
              if isinstance(filename,str):
                  filename = filename.decode('utf-8')
                  filename = filename.encode('idna')
              else:
                  filename = filename.encode('idna')
      except UnicodeError:
          pass
      if isinstance(filename,unicode):
          filename=filename.encode('utf-8')
      filemd5 = _md5(filename).hexdigest()
      filename = re_url_scheme.sub("", filename)
      filename = re_slash.sub(",", filename)
  
      # limit length of filename
      if len(filename)>200:
          filename=filename[:200]
      return ",".join((filename, filemd5))
  
  NORMALIZE_SPACE = re.compile(r'(?:\r\n)?[ \t]+')
  def _normalize_headers(headers):
      return dict([ (key.lower(), NORMALIZE_SPACE.sub(value, ' ').strip())  for (key, value) in headers.iteritems()])
  
  def _parse_cache_control(headers):
      retval = {}
      if headers.has_key('cache-control'):
          parts =  headers['cache-control'].split(',')
          parts_with_args = [tuple([x.strip().lower() for x in part.split("=", 1)]) for part in parts if -1 != part.find("=")]
          parts_wo_args = [(name.strip().lower(), 1) for name in parts if -1 == name.find("=")]
          retval = dict(parts_with_args + parts_wo_args)
      return retval
  
  # Whether to use a strict mode to parse WWW-Authenticate headers
  # Might lead to bad results in case of ill-formed header value,
  # so disabled by default, falling back to relaxed parsing.
  # Set to true to turn on, usefull for testing servers.
  USE_WWW_AUTH_STRICT_PARSING = 0
  
  # In regex below:
  #    [^\0-\x1f\x7f-\xff()<>@,;:\\\"/[\]?={} \t]+             matches a "token" as defined by HTTP
  #    "(?:[^\0-\x08\x0A-\x1f\x7f-\xff\\\"]|\\[\0-\x7f])*?"    matches a "quoted-string" as defined by HTTP, when LWS have already been replaced by a single space
  # Actually, as an auth-param value can be either a token or a quoted-string, they are combined in a single pattern which matches both:
  #    \"?((?<=\")(?:[^\0-\x1f\x7f-\xff\\\"]|\\[\0-\x7f])*?(?=\")|(?<!\")[^\0-\x08\x0A-\x1f\x7f-\xff()<>@,;:\\\"/[\]?={} \t]+(?!\"))\"?
  WWW_AUTH_STRICT = re.compile(r"^(?:\s*(?:,\s*)?([^\0-\x1f\x7f-\xff()<>@,;:\\\"/[\]?={} \t]+)\s*=\s*\"?((?<=\")(?:[^\0-\x08\x0A-\x1f\x7f-\xff\\\"]|\\[\0-\x7f])*?(?=\")|(?<!\")[^\0-\x1f\x7f-\xff()<>@,;:\\\"/[\]?={} \t]+(?!\"))\"?)(.*)$")
  WWW_AUTH_RELAXED = re.compile(r"^(?:\s*(?:,\s*)?([^ \t\r\n=]+)\s*=\s*\"?((?<=\")(?:[^\\\"]|\\.)*?(?=\")|(?<!\")[^ \t\r\n,]+(?!\"))\"?)(.*)$")
  UNQUOTE_PAIRS = re.compile(r'\\(.)')
  def _parse_www_authenticate(headers, headername='www-authenticate'):
      """Returns a dictionary of dictionaries, one dict
      per auth_scheme."""
      retval = {}
      if headers.has_key(headername):
          try:
            authenticate = headers[headername].strip()
            www_auth = USE_WWW_AUTH_STRICT_PARSING and WWW_AUTH_STRICT or WWW_AUTH_RELAXED
            while authenticate:
                # Break off the scheme at the beginning of the line
                if headername == 'authentication-info':
                    (auth_scheme, the_rest) = ('digest', authenticate)
                else:
                    (auth_scheme, the_rest) = authenticate.split(" ", 1)
                # Now loop over all the key value pairs that come after the scheme,
                # being careful not to roll into the next scheme
                match = www_auth.search(the_rest)
                auth_params = {}
                while match:
                    if match and len(match.groups()) == 3:
                        (key, value, the_rest) = match.groups()
                        auth_params[key.lower()] = UNQUOTE_PAIRS.sub(r'\1', value) # '\\'.join([x.replace('\\', '') for x in value.split('\\\\')])
                    match = www_auth.search(the_rest)
                retval[auth_scheme.lower()] = auth_params
                authenticate = the_rest.strip()
          except ValueError:
            raise MalformedHeader("WWW-Authenticate")
      return retval
  
  
  def _entry_disposition(response_headers, request_headers):
      """Determine freshness from the Date, Expires and Cache-Control headers.
  
      We don't handle the following:
  
      1. Cache-Control: max-stale
      2. Age: headers are not used in the calculations.
  
      Not that this algorithm is simpler than you might think
      because we are operating as a private (non-shared) cache.
      This lets us ignore 's-maxage'. We can also ignore
      'proxy-invalidate' since we aren't a proxy.
      We will never return a stale document as
      fresh as a design decision, and thus the non-implementation
      of 'max-stale'. This also lets us safely ignore 'must-revalidate'
      since we operate as if every server has sent 'must-revalidate'.
      Since we are private we get to ignore both 'public' and
      'private' parameters. We also ignore 'no-transform' since
      we don't do any transformations.
      The 'no-store' parameter is handled at a higher level.
      So the only Cache-Control parameters we look at are:
  
      no-cache
      only-if-cached
      max-age
      min-fresh
      """
  
      retval = "STALE"
      cc = _parse_cache_control(request_headers)
      cc_response = _parse_cache_control(response_headers)
  
      if request_headers.has_key('pragma') and request_headers['pragma'].lower().find('no-cache') != -1:
          retval = "TRANSPARENT"
          if 'cache-control' not in request_headers:
              request_headers['cache-control'] = 'no-cache'
      elif cc.has_key('no-cache'):
          retval = "TRANSPARENT"
      elif cc_response.has_key('no-cache'):
          retval = "STALE"
      elif cc.has_key('only-if-cached'):
          retval = "FRESH"
      elif response_headers.has_key('date'):
          date = calendar.timegm(email.Utils.parsedate_tz(response_headers['date']))
          now = time.time()
          current_age = max(0, now - date)
          if cc_response.has_key('max-age'):
              try:
                  freshness_lifetime = int(cc_response['max-age'])
              except ValueError:
                  freshness_lifetime = 0
          elif response_headers.has_key('expires'):
              expires = email.Utils.parsedate_tz(response_headers['expires'])
              if None == expires:
                  freshness_lifetime = 0
              else:
                  freshness_lifetime = max(0, calendar.timegm(expires) - date)
          else:
              freshness_lifetime = 0
          if cc.has_key('max-age'):
              try:
                  freshness_lifetime = int(cc['max-age'])
              except ValueError:
                  freshness_lifetime = 0
          if cc.has_key('min-fresh'):
              try:
                  min_fresh = int(cc['min-fresh'])
              except ValueError:
                  min_fresh = 0
              current_age += min_fresh
          if freshness_lifetime > current_age:
              retval = "FRESH"
      return retval
  
  def _decompressContent(response, new_content):
      content = new_content
      try:
          encoding = response.get('content-encoding', None)
          if encoding in ['gzip', 'deflate']:
              if encoding == 'gzip':
                  content = gzip.GzipFile(fileobj=StringIO.StringIO(new_content)).read()
              if encoding == 'deflate':
                  content = zlib.decompress(content)
              response['content-length'] = str(len(content))
              # Record the historical presence of the encoding in a way the won't interfere.
              response['-content-encoding'] = response['content-encoding']
              del response['content-encoding']
      except IOError:
          content = ""
          raise FailedToDecompressContent(_("Content purported to be compressed with %s but failed to decompress.") % response.get('content-encoding'), response, content)
      return content
  
  def _updateCache(request_headers, response_headers, content, cache, cachekey):
      if cachekey:
          cc = _parse_cache_control(request_headers)
          cc_response = _parse_cache_control(response_headers)
          if cc.has_key('no-store') or cc_response.has_key('no-store'):
              cache.delete(cachekey)
          else:
              info = email.Message.Message()
              for key, value in response_headers.iteritems():
                  if key not in ['status','content-encoding','transfer-encoding']:
                      info[key] = value
  
              # Add annotations to the cache to indicate what headers
              # are variant for this request.
              vary = response_headers.get('vary', None)
              if vary:
                  vary_headers = vary.lower().replace(' ', '').split(',')
                  for header in vary_headers:
                      key = '-varied-%s' % header
                      try:
                          info[key] = request_headers[header]
                      except KeyError:
                          pass
  
              status = response_headers.status
              if status == 304:
                  status = 200
  
              status_header = 'status: %d\r\n' % status
  
              header_str = info.as_string()
  
              header_str = re.sub("\r(?!\n)|(?<!\r)\n", "\r\n", header_str)
              text = "".join([status_header, header_str, content])
  
              cache.set(cachekey, text)
  
  def _cnonce():
      dig = _md5("%s:%s" % (time.ctime(), ["0123456789"[random.randrange(0, 9)] for i in range(20)])).hexdigest()
      return dig[:16]
  
  def _wsse_username_token(cnonce, iso_now, password):
      return base64.b64encode(_sha("%s%s%s" % (cnonce, iso_now, password)).digest()).strip()
  
  
  # For credentials we need two things, first
  # a pool of credential to try (not necesarily tied to BAsic, Digest, etc.)
  # Then we also need a list of URIs that have already demanded authentication
  # That list is tricky since sub-URIs can take the same auth, or the
  # auth scheme may change as you descend the tree.
  # So we also need each Auth instance to be able to tell us
  # how close to the 'top' it is.
  
  class Authentication(object):
      def __init__(self, credentials, host, request_uri, headers, response, content, http):
          (scheme, authority, path, query, fragment) = parse_uri(request_uri)
          self.path = path
          self.host = host
          self.credentials = credentials
          self.http = http
  
      def depth(self, request_uri):
          (scheme, authority, path, query, fragment) = parse_uri(request_uri)
          return request_uri[len(self.path):].count("/")
  
      def inscope(self, host, request_uri):
          # XXX Should we normalize the request_uri?
          (scheme, authority, path, query, fragment) = parse_uri(request_uri)
          return (host == self.host) and path.startswith(self.path)
  
      def request(self, method, request_uri, headers, content):
          """Modify the request headers to add the appropriate
          Authorization header. Over-rise this in sub-classes."""
          pass
  
      def response(self, response, content):
          """Gives us a chance to update with new nonces
          or such returned from the last authorized response.
          Over-rise this in sub-classes if necessary.
  
          Return TRUE is the request is to be retried, for
          example Digest may return stale=true.
          """
          return False
  
  
  
  class BasicAuthentication(Authentication):
      def __init__(self, credentials, host, request_uri, headers, response, content, http):
          Authentication.__init__(self, credentials, host, request_uri, headers, response, content, http)
  
      def request(self, method, request_uri, headers, content):
          """Modify the request headers to add the appropriate
          Authorization header."""
          headers['authorization'] = 'Basic ' + base64.b64encode("%s:%s" % self.credentials).strip()
  
  
  class DigestAuthentication(Authentication):
      """Only do qop='auth' and MD5, since that
      is all Apache currently implements"""
      def __init__(self, credentials, host, request_uri, headers, response, content, http):
          Authentication.__init__(self, credentials, host, request_uri, headers, response, content, http)
          challenge = _parse_www_authenticate(response, 'www-authenticate')
          self.challenge = challenge['digest']
          qop = self.challenge.get('qop', 'auth')
          self.challenge['qop'] = ('auth' in [x.strip() for x in qop.split()]) and 'auth' or None
          if self.challenge['qop'] is None:
              raise UnimplementedDigestAuthOptionError( _("Unsupported value for qop: %s." % qop))
          self.challenge['algorithm'] = self.challenge.get('algorithm', 'MD5').upper()
          if self.challenge['algorithm'] != 'MD5':
              raise UnimplementedDigestAuthOptionError( _("Unsupported value for algorithm: %s." % self.challenge['algorithm']))
          self.A1 = "".join([self.credentials[0], ":", self.challenge['realm'], ":", self.credentials[1]])
          self.challenge['nc'] = 1
  
      def request(self, method, request_uri, headers, content, cnonce = None):
          """Modify the request headers"""
          H = lambda x: _md5(x).hexdigest()
          KD = lambda s, d: H("%s:%s" % (s, d))
          A2 = "".join([method, ":", request_uri])
          self.challenge['cnonce'] = cnonce or _cnonce()
          request_digest  = '"%s"' % KD(H(self.A1), "%s:%s:%s:%s:%s" % (self.challenge['nonce'],
                      '%08x' % self.challenge['nc'],
                      self.challenge['cnonce'],
                      self.challenge['qop'], H(A2)
                      ))
          headers['authorization'] = 'Digest username="%s", realm="%s", nonce="%s", uri="%s", algorithm=%s, response=%s, qop=%s, nc=%08x, cnonce="%s"' % (
                  self.credentials[0],
                  self.challenge['realm'],
                  self.challenge['nonce'],
                  request_uri,
                  self.challenge['algorithm'],
                  request_digest,
                  self.challenge['qop'],
                  self.challenge['nc'],
                  self.challenge['cnonce'],
                  )
          if self.challenge.get('opaque'):
              headers['authorization'] += ', opaque="%s"' % self.challenge['opaque']
          self.challenge['nc'] += 1
  
      def response(self, response, content):
          if not response.has_key('authentication-info'):
              challenge = _parse_www_authenticate(response, 'www-authenticate').get('digest', {})
              if 'true' == challenge.get('stale'):
                  self.challenge['nonce'] = challenge['nonce']
                  self.challenge['nc'] = 1
                  return True
          else:
              updated_challenge = _parse_www_authenticate(response, 'authentication-info').get('digest', {})
  
              if updated_challenge.has_key('nextnonce'):
                  self.challenge['nonce'] = updated_challenge['nextnonce']
                  self.challenge['nc'] = 1
          return False
  
  
  class HmacDigestAuthentication(Authentication):
      """Adapted from Robert Sayre's code and DigestAuthentication above."""
      __author__ = "Thomas Broyer (t.broyer@ltgt.net)"
  
      def __init__(self, credentials, host, request_uri, headers, response, content, http):
          Authentication.__init__(self, credentials, host, request_uri, headers, response, content, http)
          challenge = _parse_www_authenticate(response, 'www-authenticate')
          self.challenge = challenge['hmacdigest']
          # TODO: self.challenge['domain']
          self.challenge['reason'] = self.challenge.get('reason', 'unauthorized')
          if self.challenge['reason'] not in ['unauthorized', 'integrity']:
              self.challenge['reason'] = 'unauthorized'
          self.challenge['salt'] = self.challenge.get('salt', '')
          if not self.challenge.get('snonce'):
              raise UnimplementedHmacDigestAuthOptionError( _("The challenge doesn't contain a server nonce, or this one is empty."))
          self.challenge['algorithm'] = self.challenge.get('algorithm', 'HMAC-SHA-1')
          if self.challenge['algorithm'] not in ['HMAC-SHA-1', 'HMAC-MD5']:
              raise UnimplementedHmacDigestAuthOptionError( _("Unsupported value for algorithm: %s." % self.challenge['algorithm']))
          self.challenge['pw-algorithm'] = self.challenge.get('pw-algorithm', 'SHA-1')
          if self.challenge['pw-algorithm'] not in ['SHA-1', 'MD5']:
              raise UnimplementedHmacDigestAuthOptionError( _("Unsupported value for pw-algorithm: %s." % self.challenge['pw-algorithm']))
          if self.challenge['algorithm'] == 'HMAC-MD5':
              self.hashmod = _md5
          else:
              self.hashmod = _sha
          if self.challenge['pw-algorithm'] == 'MD5':
              self.pwhashmod = _md5
          else:
              self.pwhashmod = _sha
          self.key = "".join([self.credentials[0], ":",
                      self.pwhashmod.new("".join([self.credentials[1], self.challenge['salt']])).hexdigest().lower(),
                      ":", self.challenge['realm']
                      ])
          self.key = self.pwhashmod.new(self.key).hexdigest().lower()
  
      def request(self, method, request_uri, headers, content):
          """Modify the request headers"""
          keys = _get_end2end_headers(headers)
          keylist = "".join(["%s " % k for k in keys])
          headers_val = "".join([headers[k] for k in keys])
          created = time.strftime('%Y-%m-%dT%H:%M:%SZ',time.gmtime())
          cnonce = _cnonce()
          request_digest = "%s:%s:%s:%s:%s" % (method, request_uri, cnonce, self.challenge['snonce'], headers_val)
          request_digest  = hmac.new(self.key, request_digest, self.hashmod).hexdigest().lower()
          headers['authorization'] = 'HMACDigest username="%s", realm="%s", snonce="%s", cnonce="%s", uri="%s", created="%s", response="%s", headers="%s"' % (
                  self.credentials[0],
                  self.challenge['realm'],
                  self.challenge['snonce'],
                  cnonce,
                  request_uri,
                  created,
                  request_digest,
                  keylist,
                  )
  
      def response(self, response, content):
          challenge = _parse_www_authenticate(response, 'www-authenticate').get('hmacdigest', {})
          if challenge.get('reason') in ['integrity', 'stale']:
              return True
          return False
  
  
  class WsseAuthentication(Authentication):
      """This is thinly tested and should not be relied upon.
      At this time there isn't any third party server to test against.
      Blogger and TypePad implemented this algorithm at one point
      but Blogger has since switched to Basic over HTTPS and
      TypePad has implemented it wrong, by never issuing a 401
      challenge but instead requiring your client to telepathically know that
      their endpoint is expecting WSSE profile="UsernameToken"."""
      def __init__(self, credentials, host, request_uri, headers, response, content, http):
          Authentication.__init__(self, credentials, host, request_uri, headers, response, content, http)
  
      def request(self, method, request_uri, headers, content):
          """Modify the request headers to add the appropriate
          Authorization header."""
          headers['authorization'] = 'WSSE profile="UsernameToken"'
          iso_now = time.strftime("%Y-%m-%dT%H:%M:%SZ", time.gmtime())
          cnonce = _cnonce()
          password_digest = _wsse_username_token(cnonce, iso_now, self.credentials[1])
          headers['X-WSSE'] = 'UsernameToken Username="%s", PasswordDigest="%s", Nonce="%s", Created="%s"' % (
                  self.credentials[0],
                  password_digest,
                  cnonce,
                  iso_now)
  
  class GoogleLoginAuthentication(Authentication):
      def __init__(self, credentials, host, request_uri, headers, response, content, http):
          from urllib import urlencode
          Authentication.__init__(self, credentials, host, request_uri, headers, response, content, http)
          challenge = _parse_www_authenticate(response, 'www-authenticate')
          service = challenge['googlelogin'].get('service', 'xapi')
          # Bloggger actually returns the service in the challenge
          # For the rest we guess based on the URI
          if service == 'xapi' and  request_uri.find("calendar") > 0:
              service = "cl"
          # No point in guessing Base or Spreadsheet
          #elif request_uri.find("spreadsheets") > 0:
          #    service = "wise"
  
          auth = dict(Email=credentials[0], Passwd=credentials[1], service=service, source=headers['user-agent'])
          resp, content = self.http.request("https://www.google.com/accounts/ClientLogin", method="POST", body=urlencode(auth), headers={'Content-Type': 'application/x-www-form-urlencoded'})
          lines = content.split('\n')
          d = dict([tuple(line.split("=", 1)) for line in lines if line])
          if resp.status == 403:
              self.Auth = ""
          else:
              self.Auth = d['Auth']
  
      def request(self, method, request_uri, headers, content):
          """Modify the request headers to add the appropriate
          Authorization header."""
          headers['authorization'] = 'GoogleLogin Auth=' + self.Auth
  
  
  AUTH_SCHEME_CLASSES = {
      "basic": BasicAuthentication,
      "wsse": WsseAuthentication,
      "digest": DigestAuthentication,
      "hmacdigest": HmacDigestAuthentication,
      "googlelogin": GoogleLoginAuthentication
  }
  
  AUTH_SCHEME_ORDER = ["hmacdigest", "googlelogin", "digest", "wsse", "basic"]
  
  class FileCache(object):
      """Uses a local directory as a store for cached files.
      Not really safe to use if multiple threads or processes are going to
      be running on the same cache.
      """
      def __init__(self, cache, safe=safename): # use safe=lambda x: md5.new(x).hexdigest() for the old behavior
          self.cache = cache
          self.safe = safe
          if not os.path.exists(cache):
              os.makedirs(self.cache)
  
      def get(self, key):
          retval = None
          cacheFullPath = os.path.join(self.cache, self.safe(key))
          try:
              f = file(cacheFullPath, "rb")
              retval = f.read()
              f.close()
          except IOError:
              pass
          return retval
  
      def set(self, key, value):
          cacheFullPath = os.path.join(self.cache, self.safe(key))
          f = file(cacheFullPath, "wb")
          f.write(value)
          f.close()
  
      def delete(self, key):
          cacheFullPath = os.path.join(self.cache, self.safe(key))
          if os.path.exists(cacheFullPath):
              os.remove(cacheFullPath)
  
  class Credentials(object):
      def __init__(self):
          self.credentials = []
  
      def add(self, name, password, domain=""):
          self.credentials.append((domain.lower(), name, password))
  
      def clear(self):
          self.credentials = []
  
      def iter(self, domain):
          for (cdomain, name, password) in self.credentials:
              if cdomain == "" or domain == cdomain:
                  yield (name, password)
  
  class KeyCerts(Credentials):
      """Identical to Credentials except that
      name/password are mapped to key/cert."""
      pass
  
  
  class ProxyInfo(object):
    """Collect information required to use a proxy."""
    def __init__(self, proxy_type, proxy_host, proxy_port, proxy_rdns=None, proxy_user=None, proxy_pass=None):
        """The parameter proxy_type must be set to one of socks.PROXY_TYPE_XXX
        constants. For example:
  
  p = ProxyInfo(proxy_type=socks.PROXY_TYPE_HTTP, proxy_host='localhost', proxy_port=8000)
        """
        self.proxy_type, self.proxy_host, self.proxy_port, self.proxy_rdns, self.proxy_user, self.proxy_pass = proxy_type, proxy_host, proxy_port, proxy_rdns, proxy_user, proxy_pass
  
    def astuple(self):
      return (self.proxy_type, self.proxy_host, self.proxy_port, self.proxy_rdns,
          self.proxy_user, self.proxy_pass)
  
    def isgood(self):
      return (self.proxy_host != None) and (self.proxy_port != None)
  
  
  class HTTPConnectionWithTimeout(httplib.HTTPConnection):
      """
      HTTPConnection subclass that supports timeouts
  
      All timeouts are in seconds. If None is passed for timeout then
      Python's default timeout for sockets will be used. See for example
      the docs of socket.setdefaulttimeout():
      http://docs.python.org/library/socket.html#socket.setdefaulttimeout
      """
  
      def __init__(self, host, port=None, strict=None, timeout=None, proxy_info=None):
          httplib.HTTPConnection.__init__(self, host, port, strict)
          self.timeout = timeout
          self.proxy_info = proxy_info
  
      def connect(self):
          """Connect to the host and port specified in __init__."""
          # Mostly verbatim from httplib.py.
          if self.proxy_info and socks is None:
              raise ProxiesUnavailableError(
                  'Proxy support missing but proxy use was requested!')
          msg = "getaddrinfo returns an empty list"
          for res in socket.getaddrinfo(self.host, self.port, 0,
                  socket.SOCK_STREAM):
              af, socktype, proto, canonname, sa = res
              try:
                  if self.proxy_info and self.proxy_info.isgood():
                      self.sock = socks.socksocket(af, socktype, proto)
                      self.sock.setproxy(*self.proxy_info.astuple())
                  else:
                      self.sock = socket.socket(af, socktype, proto)
                      self.sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
                  # Different from httplib: support timeouts.
                  if has_timeout(self.timeout):
                      self.sock.settimeout(self.timeout)
                      # End of difference from httplib.
                  if self.debuglevel > 0:
                      print "connect: (%s, %s)" % (self.host, self.port)
  
                  self.sock.connect(sa)
              except socket.error, msg:
                  if self.debuglevel > 0:
                      print 'connect fail:', (self.host, self.port)
                  if self.sock:
                      self.sock.close()
                  self.sock = None
                  continue
              break
          if not self.sock:
              raise socket.error, msg
  
  class HTTPSConnectionWithTimeout(httplib.HTTPSConnection):
      """
      This class allows communication via SSL.
  
      All timeouts are in seconds. If None is passed for timeout then
      Python's default timeout for sockets will be used. See for example
      the docs of socket.setdefaulttimeout():
      http://docs.python.org/library/socket.html#socket.setdefaulttimeout
      """
      def __init__(self, host, port=None, key_file=None, cert_file=None,
                   strict=None, timeout=None, proxy_info=None,
                   ca_certs=None, disable_ssl_certificate_validation=False):
          httplib.HTTPSConnection.__init__(self, host, port=port, key_file=key_file,
                  cert_file=cert_file, strict=strict)
          self.timeout = timeout
          self.proxy_info = proxy_info
          if ca_certs is None:
            ca_certs = CA_CERTS
          self.ca_certs = ca_certs
          self.disable_ssl_certificate_validation = \
                  disable_ssl_certificate_validation
  
      # The following two methods were adapted from https_wrapper.py, released
      # with the Google Appengine SDK at
      # http://googleappengine.googlecode.com/svn-history/r136/trunk/python/google/appengine/tools/https_wrapper.py
      # under the following license:
      #
      # Copyright 2007 Google Inc.
      #
      # Licensed under the Apache License, Version 2.0 (the "License");
      # you may not use this file except in compliance with the License.
      # You may obtain a copy of the License at
      #
      #     http://www.apache.org/licenses/LICENSE-2.0
      #
      # Unless required by applicable law or agreed to in writing, software
      # distributed under the License is distributed on an "AS IS" BASIS,
      # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      # See the License for the specific language governing permissions and
      # limitations under the License.
      #
  
      def _GetValidHostsForCert(self, cert):
          """Returns a list of valid host globs for an SSL certificate.
  
          Args:
            cert: A dictionary representing an SSL certificate.
          Returns:
            list: A list of valid host globs.
          """
          if 'subjectAltName' in cert:
              return [x[1] for x in cert['subjectAltName']
                      if x[0].lower() == 'dns']
          else:
              return [x[0][1] for x in cert['subject']
                      if x[0][0].lower() == 'commonname']
  
      def _ValidateCertificateHostname(self, cert, hostname):
          """Validates that a given hostname is valid for an SSL certificate.
  
          Args:
            cert: A dictionary representing an SSL certificate.
            hostname: The hostname to test.
          Returns:
            bool: Whether or not the hostname is valid for this certificate.
          """
          hosts = self._GetValidHostsForCert(cert)
          for host in hosts:
              host_re = host.replace('.', '\.').replace('*', '[^.]*')
              if re.search('^%s$' % (host_re,), hostname, re.I):
                  return True
          return False
  
      def connect(self):
          "Connect to a host on a given (SSL) port."
  
          msg = "getaddrinfo returns an empty list"
          for family, socktype, proto, canonname, sockaddr in socket.getaddrinfo(
              self.host, self.port, 0, socket.SOCK_STREAM):
              try:
                  if self.proxy_info and self.proxy_info.isgood():
                      sock = socks.socksocket(family, socktype, proto)
                      sock.setproxy(*self.proxy_info.astuple())
                  else:
                      sock = socket.socket(family, socktype, proto)
                      sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
  
                  if has_timeout(self.timeout):
                      sock.settimeout(self.timeout)
                  sock.connect((self.host, self.port))
                  self.sock =_ssl_wrap_socket(
                      sock, self.key_file, self.cert_file,
                      self.disable_ssl_certificate_validation, self.ca_certs)
                  if self.debuglevel > 0:
                      print "connect: (%s, %s)" % (self.host, self.port)
                  if not self.disable_ssl_certificate_validation:
                      cert = self.sock.getpeercert()
                      hostname = self.host.split(':', 0)[0]
                      if not self._ValidateCertificateHostname(cert, hostname):
                          raise CertificateHostnameMismatch(
                              'Server presented certificate that does not match '
                              'host %s: %s' % (hostname, cert), hostname, cert)
              except ssl_SSLError, e:
                  if sock:
                      sock.close()
                  if self.sock:
                      self.sock.close()
                  self.sock = None
                  # Unfortunately the ssl module doesn't seem to provide any way
                  # to get at more detailed error information, in particular
                  # whether the error is due to certificate validation or
                  # something else (such as SSL protocol mismatch).
                  if e.errno == ssl.SSL_ERROR_SSL:
                      raise SSLHandshakeError(e)
                  else:
                      raise
              except (socket.timeout, socket.gaierror):
                raise
              except socket.error, msg:
                if self.debuglevel > 0:
                    print 'connect fail:', (self.host, self.port)
                if self.sock:
                    self.sock.close()
                self.sock = None
                continue
              break
          if not self.sock:
            raise socket.error, msg
  
  SCHEME_TO_CONNECTION = {
      'http': HTTPConnectionWithTimeout,
      'https': HTTPSConnectionWithTimeout
      }
  
  # Use a different connection object for Google App Engine
  try:
    from google.appengine.api import apiproxy_stub_map
    if apiproxy_stub_map.apiproxy.GetStub('urlfetch') is None:
      raise ImportError  # Bail out; we're not actually running on App Engine.
    from google.appengine.api.urlfetch import fetch
    from google.appengine.api.urlfetch import InvalidURLError
    from google.appengine.api.urlfetch import DownloadError
    from google.appengine.api.urlfetch import ResponseTooLargeError
    from google.appengine.api.urlfetch import SSLCertificateError
  
  
    class ResponseDict(dict):
      """Is a dictionary that also has a read() method, so
      that it can pass itself off as an httlib.HTTPResponse()."""
      def read(self):
        pass
  
  
    class AppEngineHttpConnection(object):
      """Emulates an httplib.HTTPConnection object, but actually uses the Google
      App Engine urlfetch library. This allows the timeout to be properly used on
      Google App Engine, and avoids using httplib, which on Google App Engine is
      just another wrapper around urlfetch.
      """
      def __init__(self, host, port=None, key_file=None, cert_file=None,
                   strict=None, timeout=None, proxy_info=None, ca_certs=None,
                   disable_certificate_validation=False):
        self.host = host
        self.port = port
        self.timeout = timeout
        if key_file or cert_file or proxy_info or ca_certs:
          raise NotSupportedOnThisPlatform()
        self.response = None
        self.scheme = 'http'
        self.validate_certificate = not disable_certificate_validation
        self.sock = True
  
      def request(self, method, url, body, headers):
        # Calculate the absolute URI, which fetch requires
        netloc = self.host
        if self.port:
          netloc = '%s:%s' % (self.host, self.port)
        absolute_uri = '%s://%s%s' % (self.scheme, netloc, url)
        try:
          response = fetch(absolute_uri, payload=body, method=method,
              headers=headers, allow_truncated=False, follow_redirects=False,
              deadline=self.timeout,
              validate_certificate=self.validate_certificate)
          self.response = ResponseDict(response.headers)
          self.response['status'] = str(response.status_code)
          self.response.status = response.status_code
          setattr(self.response, 'read', lambda : response.content)
  
        # Make sure the exceptions raised match the exceptions expected.
        except InvalidURLError:
          raise socket.gaierror('')
        except (DownloadError, ResponseTooLargeError, SSLCertificateError):
          raise httplib.HTTPException()
  
      def getresponse(self):
        if self.response:
          return self.response
        else:
          raise httplib.HTTPException()
  
      def set_debuglevel(self, level):
        pass
  
      def connect(self):
        pass
  
      def close(self):
        pass
  
  
    class AppEngineHttpsConnection(AppEngineHttpConnection):
      """Same as AppEngineHttpConnection, but for HTTPS URIs."""
      def __init__(self, host, port=None, key_file=None, cert_file=None,
                   strict=None, timeout=None, proxy_info=None):
        AppEngineHttpConnection.__init__(self, host, port, key_file, cert_file,
            strict, timeout, proxy_info)
        self.scheme = 'https'
  
    # Update the connection classes to use the Googel App Engine specific ones.
    SCHEME_TO_CONNECTION = {
        'http': AppEngineHttpConnection,
        'https': AppEngineHttpsConnection
        }
  
  except ImportError:
    pass
  
  
  class Http(object):
      """An HTTP client that handles:
  - all methods
  - caching
  - ETags
  - compression,
  - HTTPS
  - Basic
  - Digest
  - WSSE
  
  and more.
      """
      def __init__(self, cache=None, timeout=None, proxy_info=None,
                   ca_certs=None, disable_ssl_certificate_validation=False):
          """
          The value of proxy_info is a ProxyInfo instance.
  
          If 'cache' is a string then it is used as a directory name for
          a disk cache. Otherwise it must be an object that supports the
          same interface as FileCache.
  
          All timeouts are in seconds. If None is passed for timeout
          then Python's default timeout for sockets will be used. See
          for example the docs of socket.setdefaulttimeout():
          http://docs.python.org/library/socket.html#socket.setdefaulttimeout
  
          ca_certs is the path of a file containing root CA certificates for SSL
          server certificate validation.  By default, a CA cert file bundled with
          httplib2 is used.
  
          If disable_ssl_certificate_validation is true, SSL cert validation will
          not be performed.
          """
          self.proxy_info = proxy_info
          self.ca_certs = ca_certs
          self.disable_ssl_certificate_validation = \
                  disable_ssl_certificate_validation
  
          # Map domain name to an httplib connection
          self.connections = {}
          # The location of the cache, for now a directory
          # where cached responses are held.
          if cache and isinstance(cache, basestring):
              self.cache = FileCache(cache)
          else:
              self.cache = cache
  
          # Name/password
          self.credentials = Credentials()
  
          # Key/cert
          self.certificates = KeyCerts()
  
          # authorization objects
          self.authorizations = []
  
          # If set to False then no redirects are followed, even safe ones.
          self.follow_redirects = True
  
          # Which HTTP methods do we apply optimistic concurrency to, i.e.
          # which methods get an "if-match:" etag header added to them.
          self.optimistic_concurrency_methods = ["PUT", "PATCH"]
  
          # If 'follow_redirects' is True, and this is set to True then
          # all redirecs are followed, including unsafe ones.
          self.follow_all_redirects = False
  
          self.ignore_etag = False
  
          self.force_exception_to_status_code = False
  
          self.timeout = timeout
  
      def _auth_from_challenge(self, host, request_uri, headers, response, content):
          """A generator that creates Authorization objects
             that can be applied to requests.
          """
          challenges = _parse_www_authenticate(response, 'www-authenticate')
          for cred in self.credentials.iter(host):
              for scheme in AUTH_SCHEME_ORDER:
                  if challenges.has_key(scheme):
                      yield AUTH_SCHEME_CLASSES[scheme](cred, host, request_uri, headers, response, content, self)
  
      def add_credentials(self, name, password, domain=""):
          """Add a name and password that will be used
          any time a request requires authentication."""
          self.credentials.add(name, password, domain)
  
      def add_certificate(self, key, cert, domain):
          """Add a key and cert that will be used
          any time a request requires authentication."""
          self.certificates.add(key, cert, domain)
  
      def clear_credentials(self):
          """Remove all the names and passwords
          that are used for authentication"""
          self.credentials.clear()
          self.authorizations = []
  
      def _conn_request(self, conn, request_uri, method, body, headers):
          for i in range(2):
              try:
                  if conn.sock is None:
                    conn.connect()
                  conn.request(method, request_uri, body, headers)
              except socket.timeout:
                  raise
              except socket.gaierror:
                  conn.close()
                  raise ServerNotFoundError("Unable to find the server at %s" % conn.host)
              except ssl_SSLError:
                  conn.close()
                  raise
              except socket.error, e:
                  err = 0
                  if hasattr(e, 'args'):
                      err = getattr(e, 'args')[0]
                  else:
                      err = e.errno
                  if err == errno.ECONNREFUSED: # Connection refused
                      raise
              except httplib.HTTPException:
                  # Just because the server closed the connection doesn't apparently mean
                  # that the server didn't send a response.
                  if conn.sock is None:
                      if i == 0:
                          conn.close()
                          conn.connect()
                          continue
                      else:
                          conn.close()
                          raise
                  if i == 0:
                      conn.close()
                      conn.connect()
                      continue
              try:
                  response = conn.getresponse()
              except (socket.error, httplib.HTTPException):
                  if i == 0:
                      conn.close()
                      conn.connect()
                      continue
                  else:
                      raise
              else:
                  content = ""
                  if method == "HEAD":
                      response.close()
                  else:
                      content = response.read()
                  response = Response(response)
                  if method != "HEAD":
                      content = _decompressContent(response, content)
              break
          return (response, content)
  
  
      def _request(self, conn, host, absolute_uri, request_uri, method, body, headers, redirections, cachekey):
          """Do the actual request using the connection object
          and also follow one level of redirects if necessary"""
  
          auths = [(auth.depth(request_uri), auth) for auth in self.authorizations if auth.inscope(host, request_uri)]
          auth = auths and sorted(auths)[0][1] or None
          if auth:
              auth.request(method, request_uri, headers, body)
  
          (response, content) = self._conn_request(conn, request_uri, method, body, headers)
  
          if auth:
              if auth.response(response, body):
                  auth.request(method, request_uri, headers, body)
                  (response, content) = self._conn_request(conn, request_uri, method, body, headers )
                  response._stale_digest = 1
  
          if response.status == 401:
              for authorization in self._auth_from_challenge(host, request_uri, headers, response, content):
                  authorization.request(method, request_uri, headers, body)
                  (response, content) = self._conn_request(conn, request_uri, method, body, headers, )
                  if response.status != 401:
                      self.authorizations.append(authorization)
                      authorization.response(response, body)
                      break
  
          if (self.follow_all_redirects or (method in ["GET", "HEAD"]) or response.status == 303):
              if self.follow_redirects and response.status in [300, 301, 302, 303, 307]:
                  # Pick out the location header and basically start from the beginning
                  # remembering first to strip the ETag header and decrement our 'depth'
                  if redirections:
                      if not response.has_key('location') and response.status != 300:
                          raise RedirectMissingLocation( _("Redirected but the response is missing a Location: header."), response, content)
                      # Fix-up relative redirects (which violate an RFC 2616 MUST)
                      if response.has_key('location'):
                          location = response['location']
                          (scheme, authority, path, query, fragment) = parse_uri(location)
                          if authority == None:
                              response['location'] = urlparse.urljoin(absolute_uri, location)
                      if response.status == 301 and method in ["GET", "HEAD"]:
                          response['-x-permanent-redirect-url'] = response['location']
                          if not response.has_key('content-location'):
                              response['content-location'] = absolute_uri
                          _updateCache(headers, response, content, self.cache, cachekey)
                      if headers.has_key('if-none-match'):
                          del headers['if-none-match']
                      if headers.has_key('if-modified-since'):
                          del headers['if-modified-since']
                      if response.has_key('location'):
                          location = response['location']
                          old_response = copy.deepcopy(response)
                          if not old_response.has_key('content-location'):
                              old_response['content-location'] = absolute_uri
                          redirect_method = method
                          if response.status in [302, 303]:
                              redirect_method = "GET"
                              body = None
                          (response, content) = self.request(location, redirect_method, body=body, headers = headers, redirections = redirections - 1)
                          response.previous = old_response
                  else:
                      raise RedirectLimit("Redirected more times than rediection_limit allows.", response, content)
              elif response.status in [200, 203] and method in ["GET", "HEAD"]:
                  # Don't cache 206's since we aren't going to handle byte range requests
                  if not response.has_key('content-location'):
                      response['content-location'] = absolute_uri
                  _updateCache(headers, response, content, self.cache, cachekey)
  
          return (response, content)
  
      def _normalize_headers(self, headers):
          return _normalize_headers(headers)
  
  # Need to catch and rebrand some exceptions
  # Then need to optionally turn all exceptions into status codes
  # including all socket.* and httplib.* exceptions.
  
  
      def request(self, uri, method="GET", body=None, headers=None, redirections=DEFAULT_MAX_REDIRECTS, connection_type=None):
          """ Performs a single HTTP request.
  The 'uri' is the URI of the HTTP resource and can begin
  with either 'http' or 'https'. The value of 'uri' must be an absolute URI.
  
  The 'method' is the HTTP method to perform, such as GET, POST, DELETE, etc.
  There is no restriction on the methods allowed.
  
  The 'body' is the entity body to be sent with the request. It is a string
  object.
  
  Any extra headers that are to be sent with the request should be provided in the
  'headers' dictionary.
  
  The maximum number of redirect to follow before raising an
  exception is 'redirections. The default is 5.
  
  The return value is a tuple of (response, content), the first
  being and instance of the 'Response' class, the second being
  a string that contains the response entity body.
          """
          try:
              if headers is None:
                  headers = {}
              else:
                  headers = self._normalize_headers(headers)
  
              if not headers.has_key('user-agent'):
                  headers['user-agent'] = "Python-httplib2/%s (gzip)" % __version__
  
              uri = iri2uri(uri)
  
              (scheme, authority, request_uri, defrag_uri) = urlnorm(uri)
              domain_port = authority.split(":")[0:2]
              if len(domain_port) == 2 and domain_port[1] == '443' and scheme == 'http':
                  scheme = 'https'
                  authority = domain_port[0]
  
              conn_key = scheme+":"+authority
              if conn_key in self.connections:
                  conn = self.connections[conn_key]
              else:
                  if not connection_type:
                    connection_type = SCHEME_TO_CONNECTION[scheme]
                  certs = list(self.certificates.iter(authority))
                  if issubclass(connection_type, HTTPSConnectionWithTimeout):
                      if certs:
                          conn = self.connections[conn_key] = connection_type(
                                  authority, key_file=certs[0][0],
                                  cert_file=certs[0][1], timeout=self.timeout,
                                  proxy_info=self.proxy_info,
                                  ca_certs=self.ca_certs,
                                  disable_ssl_certificate_validation=
                                          self.disable_ssl_certificate_validation)
                      else:
                          conn = self.connections[conn_key] = connection_type(
                                  authority, timeout=self.timeout,
                                  proxy_info=self.proxy_info,
                                  ca_certs=self.ca_certs,
                                  disable_ssl_certificate_validation=
                                          self.disable_ssl_certificate_validation)
                  else:
                      conn = self.connections[conn_key] = connection_type(
                              authority, timeout=self.timeout,
                              proxy_info=self.proxy_info)
                  conn.set_debuglevel(debuglevel)
  
              if 'range' not in headers and 'accept-encoding' not in headers:
                  headers['accept-encoding'] = 'gzip, deflate'
  
              info = email.Message.Message()
              cached_value = None
              if self.cache:
                  cachekey = defrag_uri
                  cached_value = self.cache.get(cachekey)
                  if cached_value:
                      # info = email.message_from_string(cached_value)
                      #
                      # Need to replace the line above with the kludge below
                      # to fix the non-existent bug not fixed in this
                      # bug report: http://mail.python.org/pipermail/python-bugs-list/2005-September/030289.html
                      try:
                          info, content = cached_value.split('\r\n\r\n', 1)
                          feedparser = email.FeedParser.FeedParser()
                          feedparser.feed(info)
                          info = feedparser.close()
                          feedparser._parse = None
                      except IndexError:
                          self.cache.delete(cachekey)
                          cachekey = None
                          cached_value = None
              else:
                  cachekey = None
  
              if method in self.optimistic_concurrency_methods and self.cache and info.has_key('etag') and not self.ignore_etag and 'if-match' not in headers:
                  # http://www.w3.org/1999/04/Editing/
                  headers['if-match'] = info['etag']
  
              if method not in ["GET", "HEAD"] and self.cache and cachekey:
                  # RFC 2616 Section 13.10
                  self.cache.delete(cachekey)
  
              # Check the vary header in the cache to see if this request
              # matches what varies in the cache.
              if method in ['GET', 'HEAD'] and 'vary' in info:
                  vary = info['vary']
                  vary_headers = vary.lower().replace(' ', '').split(',')
                  for header in vary_headers:
                      key = '-varied-%s' % header
                      value = info[key]
                      if headers.get(header, None) != value:
                              cached_value = None
                              break
  
              if cached_value and method in ["GET", "HEAD"] and self.cache and 'range' not in headers:
                  if info.has_key('-x-permanent-redirect-url'):
                      # Should cached permanent redirects be counted in our redirection count? For now, yes.
                      if redirections <= 0:
                        raise RedirectLimit("Redirected more times than rediection_limit allows.", {}, "")
                      (response, new_content) = self.request(info['-x-permanent-redirect-url'], "GET", headers = headers, redirections = redirections - 1)
                      response.previous = Response(info)
                      response.previous.fromcache = True
                  else:
                      # Determine our course of action:
                      #   Is the cached entry fresh or stale?
                      #   Has the client requested a non-cached response?
                      #
                      # There seems to be three possible answers:
                      # 1. [FRESH] Return the cache entry w/o doing a GET
                      # 2. [STALE] Do the GET (but add in cache validators if available)
                      # 3. [TRANSPARENT] Do a GET w/o any cache validators (Cache-Control: no-cache) on the request
                      entry_disposition = _entry_disposition(info, headers)
  
                      if entry_disposition == "FRESH":
                          if not cached_value:
                              info['status'] = '504'
                              content = ""
                          response = Response(info)
                          if cached_value:
                              response.fromcache = True
                          return (response, content)
  
                      if entry_disposition == "STALE":
                          if info.has_key('etag') and not self.ignore_etag and not 'if-none-match' in headers:
                              headers['if-none-match'] = info['etag']
                          if info.has_key('last-modified') and not 'last-modified' in headers:
                              headers['if-modified-since'] = info['last-modified']
                      elif entry_disposition == "TRANSPARENT":
                          pass
  
                      (response, new_content) = self._request(conn, authority, uri, request_uri, method, body, headers, redirections, cachekey)
  
                  if response.status == 304 and method == "GET":
                      # Rewrite the cache entry with the new end-to-end headers
                      # Take all headers that are in response
                      # and overwrite their values in info.
                      # unless they are hop-by-hop, or are listed in the connection header.
  
                      for key in _get_end2end_headers(response):
                          info[key] = response[key]
                      merged_response = Response(info)
                      if hasattr(response, "_stale_digest"):
                          merged_response._stale_digest = response._stale_digest
                      _updateCache(headers, merged_response, content, self.cache, cachekey)
                      response = merged_response
                      response.status = 200
                      response.fromcache = True
  
                  elif response.status == 200:
                      content = new_content
                  else:
                      self.cache.delete(cachekey)
                      content = new_content
              else:
                  cc = _parse_cache_control(headers)
                  if cc.has_key('only-if-cached'):
                      info['status'] = '504'
                      response = Response(info)
                      content = ""
                  else:
                      (response, content) = self._request(conn, authority, uri, request_uri, method, body, headers, redirections, cachekey)
          except Exception, e:
              if self.force_exception_to_status_code:
                  if isinstance(e, HttpLib2ErrorWithResponse):
                      response = e.response
                      content = e.content
                      response.status = 500
                      response.reason = str(e)
                  elif isinstance(e, socket.timeout):
                      content = "Request Timeout"
                      response = Response( {
                              "content-type": "text/plain",
                              "status": "408",
                              "content-length": len(content)
                              })
                      response.reason = "Request Timeout"
                  else:
                      content = str(e)
                      response = Response( {
                              "content-type": "text/plain",
                              "status": "400",
                              "content-length": len(content)
                              })
                      response.reason = "Bad Request"
              else:
                  raise
  
  
          return (response, content)
  
  
  
  class Response(dict):
      """An object more like email.Message than httplib.HTTPResponse."""
  
      """Is this response from our local cache"""
      fromcache = False
  
      """HTTP protocol version used by server. 10 for HTTP/1.0, 11 for HTTP/1.1. """
      version = 11
  
      "Status code returned by server. "
      status = 200
  
      """Reason phrase returned by server."""
      reason = "Ok"
  
      previous = None
  
      def __init__(self, info):
          # info is either an email.Message or
          # an httplib.HTTPResponse object.
          if isinstance(info, httplib.HTTPResponse):
              for key, value in info.getheaders():
                  self[key.lower()] = value
              self.status = info.status
              self['status'] = str(self.status)
              self.reason = info.reason
              self.version = info.version
          elif isinstance(info, email.Message.Message):
              for key, value in info.items():
                  self[key] = value
              self.status = int(self['status'])
          else:
              for key, value in info.iteritems():
                  self[key] = value
              self.status = int(self.get('status', self.status))
  
  
      def __getattr__(self, name):
          if name == 'dict':
              return self
          else:
              raise AttributeError, name
  