title: No module named pip.req
body: <p>I am installing tweepy, but I am running into an error about pip.req. I have pip installed, but for  some reason pip.req still can't be found. I did a bunch of research online and the most I could find was some issue about incompatibilities between zapo (?) and python 2.7 causing the same error for some other user. The discussion was unclear about how to solve the problem, though. Thanks!</p>
  
  <pre><code>$ python2 setup.py install
  Traceback (most recent call last):
    File "setup.py", line 5, in &lt;module&gt;
      from pip.req import parse_requirements
  ImportError: No module named pip.req
  </code></pre>