title: Heroku fails on install pip requirements
body: <p>Something very strange is happening in Heroku, I normally install my packages when I do a git push heroku master, but now what worked for months for me not work anymore.</p>
  
  <p>Here is the error:</p>
  
  <pre><code>remote: -----&gt; Python app detected
  remote: -----&gt; Installing pip
  remote: -----&gt; Installing requirements with pip
  remote:        Obtaining django-widget-tweaks from git+https://github.com/julianogouveia/django-widget-tweaks/#egg=django-widget-tweaks (from -r /tmp/build_843fc05109f047351641f1b9e1db069d/requirements.txt (line 2))
  remote:          Cloning https://github.com/julianogouveia/django-widget-tweaks/ to /app/.heroku/src/django-widget-tweaks
  remote:            Complete output from command python setup.py egg_info:
  remote:            usage: -c [global_opts] cmd1 [cmd1_opts] [cmd2 [cmd2_opts] ...]
  remote:               or: -c --help [cmd1 cmd2 ...]
  remote:               or: -c --help-commands
  remote:               or: -c cmd --help
  remote:            
  remote:            error: invalid command 'egg_info'
  remote:            
  remote:            ----------------------------------------
  remote:        Command "python setup.py egg_info" failed with error code 1 in /app/.heroku/src/django-widget-tweaks/
  remote:  !     Push rejected, failed to compile Python app.
  remote: 
  remote:  !     Push failed
  remote: Verifying deploy...
  remote: 
  remote: !   Push rejected to partnersbit-prod.
  </code></pre>
  
  <p>What is more crazy about is that the egg_info error is a setuptools pip error, and the heroku always use the last version of pip with setuptools.</p>
  
  <p>Someone has a ideia to how to start debugging this on heroku? The heroku documentation doesn't say anything about this and the stackoverflow already opened issue about this problem is incomplete and not well documented.</p>