Eu recebo esse erro sempre que tento instalar qualquer módulo usando o pip, mas o easy_install funciona perfeitamente. Não tenho proxies configurados na minha máquina Ubuntu 12.04. Anteriormente, estava funcionando bem, apenas não sabia, como parou de funcionar de repente.

Este é um erro que recebo enquanto estiver executandosudo pip install <any_package_name>:

Exception:
Traceback (most recent call last):
  File "/tmp/tmpOA61D3/pip.zip/pip/basecommand.py", line 246, in main
    status = self.run(options, args)
  File "/tmp/tmpOA61D3/pip.zip/pip/commands/install.py", line 342, in run
    requirement_set.prepare_files(finder)
  File "/tmp/tmpOA61D3/pip.zip/pip/req/req_set.py", line 345, in prepare_files
    functools.partial(self._prepare_file, finder))
  File "/tmp/tmpOA61D3/pip.zip/pip/req/req_set.py", line 290, in _walk_req_to_install
    more_reqs = handler(req_to_install)
  File "/tmp/tmpOA61D3/pip.zip/pip/req/req_set.py", line 415, in _prepare_file
    req_to_install, finder)
  File "/tmp/tmpOA61D3/pip.zip/pip/req/req_set.py", line 376, in _check_skip_installed
    finder.find_requirement(req_to_install, self.upgrade)
  File "/tmp/tmpOA61D3/pip.zip/pip/index.py", line 425, in find_requirement
    all_versions = self._find_all_versions(req.name)
  File "/tmp/tmpOA61D3/pip.zip/pip/index.py", line 349, in _find_all_versions
    index_locations = self._get_index_urls_locations(project_name)
  File "/tmp/tmpOA61D3/pip.zip/pip/index.py", line 323, in _get_index_urls_locations
    page = self._get_page(main_index_url)
  File "/tmp/tmpOA61D3/pip.zip/pip/index.py", line 789, in _get_page
    return HTMLPage.get_page(link, session=self.session)
  File "/tmp/tmpOA61D3/pip.zip/pip/index.py", line 878, in get_page
    "Cache-Control": "max-age=600",
  File "/tmp/tmpOA61D3/pip.zip/pip/_vendor/requests/sessions.py", line 476, in get
    return self.request('GET', url, **kwargs)
  File "/tmp/tmpOA61D3/pip.zip/pip/download.py", line 367, in request
    return super(PipSession, self).request(method, url, *args, **kwargs)
  File "/tmp/tmpOA61D3/pip.zip/pip/_vendor/requests/sessions.py", line 464, in request
    resp = self.send(prep, **send_kwargs)
  File "/tmp/tmpOA61D3/pip.zip/pip/_vendor/requests/sessions.py", line 576, in send
    r = adapter.send(request, **kwargs)
  File "/tmp/tmpOA61D3/pip.zip/pip/_vendor/cachecontrol/adapter.py", line 46, in send
    resp = super(CacheControlAdapter, self).send(request, **kw)
  File "/tmp/tmpOA61D3/pip.zip/pip/_vendor/requests/adapters.py", line 370, in send
    timeout=timeout
  File "/tmp/tmpOA61D3/pip.zip/pip/_vendor/requests/packages/urllib3/connectionpool.py", line 544, in urlopen
    body=body, headers=headers)
  File "/tmp/tmpOA61D3/pip.zip/pip/_vendor/requests/packages/urllib3/connectionpool.py", line 341, in _make_request
    self._validate_conn(conn)
  File "/tmp/tmpOA61D3/pip.zip/pip/_vendor/requests/packages/urllib3/connectionpool.py", line 762, in _validate_conn
    conn.connect()
  File "/tmp/tmpOA61D3/pip.zip/pip/_vendor/requests/packages/urllib3/connection.py", line 238, in connect
    ssl_version=resolved_ssl_version)
  File "/tmp/tmpOA61D3/pip.zip/pip/_vendor/requests/packages/urllib3/contrib/pyopenssl.py", line 296, in ssl_wrap_socket
    cnx.set_tlsext_host_name(server_hostname)
AttributeError: '_socketobject' object has no attribute 'set_tlsext_host_name'