title: pip3 can't install anything due to some reason about ssl
body: <p>After upgrading my ubuntu server 16.04, I can't install modules with pip3 for my python3.6. This is what I get when I try to install tensorflow-gpu for python3:</p>
  
  <pre><code>root@amax:~# pip3 install tensorflow-gpu
  pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available.
  Collecting tensorflow-gpu
    Could not fetch URL https://pypi.python.org/simple/tensorflow-gpu/: There was a problem confirming the ssl certificate: Can't connect to HTTPS URL because the SSL module is not available. - skipping
    Could not find a version that satisfies the requirement tensorflow-gpu (from versions: )
  No matching distribution found for tensorflow-gpu
  </code></pre>
  
  <p>This is my python3 and pip3 version:</p>
  
  <pre><code>root@amax:~# python3 -V
  Python 3.6.1
  root@amax:~# which python3
  /usr/local/bin/python3
  root@amax:~# pip3 -V
  pip 9.0.1 from /usr/local/lib/python3.6/site-packages (python 3.6)
  </code></pre>
  
  <p>I am sure that the openssl is installed on my server:</p>
  
  <pre><code>root@amax:~# apt -y install openssl libssl-dev
  Reading package lists... Done
  Building dependency tree       
  Reading state information... Done
  libssl-dev is already the newest version (1.0.2g-1ubuntu13).
  openssl is already the newest version (1.0.2g-1ubuntu13).
  </code></pre>
  
  <p>I think the cause of the problem might be the version of my pip3 doesn't match the openssl version. What should I do? Any suggestions will be appreciated! Thank you!</p>