title: pip error after upgrading pip & scrapy by "pip install --upgrade"
body: <p>Using debian 8(jessie) amd64 with python 2.7.9. I tried following commands:</p>
  
  <pre><code>pip install --upgrade pip
  
  pip install --upgrade scrapy
  </code></pre>
  
  <p>after that, I am getting following pip error</p>
  
  <pre><code>root@debian:~# pip
  Traceback (most recent call last):
  File "/usr/local/bin/pip", line 11, in &lt;module&gt;
  load_entry_point('pip==8.1.2', 'console_scripts', 'pip')()
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 567, in load_entry_point
  return get_distribution(dist).load_entry_point(group, name)
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2604, in load_entry_point
  return ep.load()
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2264, in load
  return self.resolve()
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2270, in resolve
  module = __import__(self.module_name, fromlist=['__name__'], level=0)
  File "/usr/local/lib/python2.7/dist-packages/pip/__init__.py", line 16, in &lt;module&gt;
  from pip.vcs import git, mercurial, subversion, bazaar  # noqa
  File "/usr/local/lib/python2.7/dist-packages/pip/vcs/mercurial.py", line 9, in &lt;module&gt;
  from pip.download import path_to_url
  File "/usr/local/lib/python2.7/dist-packages/pip/download.py", line 39, in &lt;module&gt;
  from pip._vendor import requests, six
  File "/usr/local/lib/python2.7/dist-packages/pip/_vendor/requests/__init__.py", line 53, in &lt;module&gt;
  from .packages.urllib3.contrib import pyopenssl
  File "/usr/local/lib/python2.7/dist-packages/pip/_vendor/requests/packages/urllib3/contrib/pyopenssl.py", line 54, in &lt;module&gt;
  import OpenSSL.SSL
  File "/usr/lib/python2.7/dist-packages/OpenSSL/__init__.py", line 8, in &lt;module&gt;
  from OpenSSL import rand, crypto, SSL
  File "/usr/lib/python2.7/dist-packages/OpenSSL/rand.py", line 11, in &lt;module&gt;
  from OpenSSL._util import (
  File "/usr/lib/python2.7/dist-packages/OpenSSL/_util.py", line 4, in &lt;module&gt;
  binding = Binding()
  File "/usr/lib/python2.7/dist-packages/cryptography/hazmat/bindings/openssl/binding.py", line 89, in __init__
  self._ensure_ffi_initialized()
  File "/usr/lib/python2.7/dist-packages/cryptography/hazmat/bindings/openssl/binding.py", line 113, in _ensure_ffi_initialized
  libraries=libraries,
  File "/usr/lib/python2.7/dist-packages/cryptography/hazmat/bindings/utils.py", line 80, in build_ffi
  extra_link_args=extra_link_args,
  File "/usr/local/lib/python2.7/dist-packages/cffi/api.py", line 437, in verify
  lib = self.verifier.load_library()
  File "/usr/local/lib/python2.7/dist-packages/cffi/verifier.py", line 114, in load_library
  return self._load_library()
  File "/usr/local/lib/python2.7/dist-packages/cffi/verifier.py", line 225, in _load_library
  return self._vengine.load_library()
  File "/usr/local/lib/python2.7/dist-packages/cffi/vengine_cpy.py", line 174, in load_library
  lst = list(map(self.ffi._get_cached_btype, lst))
  File "/usr/local/lib/python2.7/dist-packages/cffi/api.py", line 409, in _get_cached_btype
  BType = type.get_cached_btype(self, finishlist)
  File "/usr/local/lib/python2.7/dist-packages/cffi/model.py", line 61, in get_cached_btype
  BType = self.build_backend_type(ffi, finishlist)
  File "/usr/local/lib/python2.7/dist-packages/cffi/model.py", line 507, in build_backend_type
  base_btype = self.build_baseinttype(ffi, finishlist)
  File "/usr/local/lib/python2.7/dist-packages/cffi/model.py", line 525, in build_baseinttype
  % self._get_c_name())
  cffi.api.CDefError: 'point_conversion_form_t' has no values explicitly defined: refusing to guess which integer type it is meant to be (unsigned/signed, int/long)
  </code></pre>
  
  <p>googled for several similar problem, cffi or cryptography may cause this problem, but i can't find any clear way to fix it.</p>