title: A detailed description on virtualenv's packaging dependecies? (pip, easy_install, wheel, setuptools, distlib, etc.)
body: <p>I was working on a bugfix for Python's virtualenv, regarding very long shebang lines that are breaking things. In the process, I realized that if I want really fix to my particular issue it likely needs to be done on the lower level of Python package management. I started with pip, moved to setuptools and now set my sight on distlib.</p>
  
  <p>Can someone describe the specific dependencies of all the <em>packaging</em> libraries that <code>virtualenv</code> uses? And the dependencies between them?</p>
  
  <p>I believe that virtualenv directly imports <code>pip</code>, <code>easy_install</code> and <code>wheel</code>. Those in turn import <code>setuptools</code> and <code>distlib</code>. Am I so lucky as to assume that distlib in the lowest-level library used by all the rest in virtualenv for packages?</p>