title: python setup.py develop not updating easy_install.pth
body: <p>According to <a href="http://peak.telecommunity.com/DevCenter/setuptools#development-mode" rel="nofollow noreferrer">setuptools</a> documentation, setup.py develop is supposed to create the egg-link file and update easy_install.pth when installing into site-packages folder.  However, in my case it's only creating the egg-link file.  How does setuptools decide if it needs to update easy_install.pth?</p>
  
  <p>Some more info:
  It works when I have setuptools 0.6c7 installed as a folder under site-packages.  But when I use setuptools 0.6c9 installed as a zipped egg, it does not work.</p>