title: pip is showing error after downloading OPENSSL
body: <p>pip command is showing error.
  i downloaded libraries from <a href="https://github.com/rajpaul/igotoeurope/blob/master/requirements.txt" rel="nofollow noreferrer">https://github.com/rajpaul/igotoeurope/blob/master/requirements.txt</a> then it started showing error in pip. i tried uninstalling the pip command and reinstalling the same still it didn't work.             </p>
  
  <p>Traceback (most recent call last):
            File "/usr/lib/python3/dist-packages/pip/_vendor/<strong>init</strong>.py", line 33, in vendored
              <strong>import</strong>(vendored_name, globals(), locals(), level=0)
          ModuleNotFoundError: No module named 'pip._vendor.cachecontrol'</p>
  
  <pre><code>During handling of the above exception, another exception occurred:
  
  Traceback (most recent call last):
    File "/usr/bin/pip3", line 9, in &lt;module&gt;
      from pip import main
    File "/usr/lib/python3/dist-packages/pip/__init__.py", line 22, in &lt;module&gt;
      from pip._vendor.requests.packages.urllib3.exceptions import DependencyWarning
  
    File "/usr/lib/python3/dist-packages/pip/_vendor/__init__.py", line 64, in &lt;module&gt;
      vendored("cachecontrol")
    File "/usr/lib/python3/dist-packages/pip/_vendor/__init__.py", line 36, in vendored
      __import__(modulename, globals(), locals(), level=0)
    File "&lt;frozen importlib._bootstrap&gt;", line 971, in _find_and_load
    File "&lt;frozen importlib._bootstrap&gt;", line 955, in _find_and_load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 656, in _load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 626, in _load_backward_compatible
    File "/usr/share/python-wheels/CacheControl-0.11.7-py2.py3-none-any.whl/cachecontrol/__init__.py", line 9, in &lt;module&gt;
    File "&lt;frozen importlib._bootstrap&gt;", line 971, in _find_and_load
    File "&lt;frozen importlib._bootstrap&gt;", line 955, in _find_and_load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 656, in _load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 626, in _load_backward_compatible
    File "/usr/share/python-wheels/CacheControl-0.11.7-py2.py3-none-any.whl/cachecontrol/wrapper.py", line 1, in &lt;module&gt;
    File "&lt;frozen importlib._bootstrap&gt;", line 971, in _find_and_load
    File "&lt;frozen importlib._bootstrap&gt;", line 955, in _find_and_load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 656, in _load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 626, in _load_backward_compatible
    File "/usr/share/python-wheels/CacheControl-0.11.7-py2.py3-none-any.whl/cachecontrol/adapter.py", line 4, in &lt;module&gt;
    File "&lt;frozen importlib._bootstrap&gt;", line 971, in _find_and_load
    File "&lt;frozen importlib._bootstrap&gt;", line 955, in _find_and_load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 656, in _load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 626, in _load_backward_compatible
    File "/usr/share/python-wheels/requests-2.18.4-py2.py3-none-any.whl/requests/__init__.py", line 84, in &lt;module&gt;
    File "&lt;frozen importlib._bootstrap&gt;", line 971, in _find_and_load
    File "&lt;frozen importlib._bootstrap&gt;", line 955, in _find_and_load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 656, in _load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 626, in _load_backward_compatible
    File "/usr/share/python-wheels/urllib3-1.22-py2.py3-none-any.whl/urllib3/contrib/pyopenssl.py", line 46, in &lt;module&gt;
    File "/home/aaroosh/.local/lib/python3.6/site-packages/OpenSSL/__init__.py", line 8, in &lt;module&gt;
      from OpenSSL import rand, crypto, SSL
    File "/home/aaroosh/.local/lib/python3.6/site-packages/OpenSSL/rand.py", line 11, in &lt;module&gt;
      from OpenSSL._util import (
    File "/home/aaroosh/.local/lib/python3.6/site-packages/OpenSSL/_util.py", line 3, in &lt;module&gt;
      from cryptography.hazmat.bindings.openssl.binding import Binding
    File "/home/aaroosh/.local/lib/python3.6/site-packages/cryptography/hazmat/bindings/openssl/binding.py", line 13, in &lt;module&gt;
      from cryptography.hazmat.bindings._openssl import ffi, lib
  AttributeError: module '_cffi_backend' has no attribute '_init_cffi_1_0_external_module'
  </code></pre>