title: Python asks for older paths on mac after deleting duplicate python installation
body: <p>I am having the below error after a clean installation of python via brew install python. The link belongs to a previous python installation which I deleted manually.</p>
  
  <pre><code>$ virtualenv ENV
  python: posix_spawn: /System/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python: No such file or directory
  </code></pre>
  
  <p>I am using MacOS 10.7.3 and I installed virtualenv via pip:</p>
  
  <pre><code>$ sudo /usr/local/share/python/pip install virtualenv
   Downloading/unpacking virtualenv
   Downloading virtualenv-1.7.1.2.tar.gz (2.1Mb): 2.1Mb downloaded
   Running setup.py egg_info for package virtualenv
  
   warning: no previously-included files matching '*.*' found under directory 'docs/_templates'
   Installing collected packages: virtualenv
   Running setup.py install for virtualenv
  
   warning: no previously-included files matching '*.*' found under directory 'docs/_templates'
   Installing virtualenv script to /usr/local/share/python
   Successfully installed virtualenv
   Cleaning up...
  $ virtualenv ENV
   python: posix_spawn: /System/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python: No such file or directory
  </code></pre>
  
  <p>How can I fix this?</p>
  
  <p>Edit : I reinstalled MacOSx and now returned back to my previous status that made me delete the preinstalled python.</p>
  
  <pre><code>$ which python 
  /Library/Frameworks/Python.framework/Versions/2.7/bin/python 
  $ which pip /usr/local/bin/pip $ sudo pip install virtualenv
  Downloading/unpacking virtualenv 
  Downloading virtualenv-1.7.1.2.tar.gz (2.1Mb): 2.1Mb downloaded
  Running setup.py egg_info for package virtualenv
  
  warning: no previously-included files matching '*.*' found under directory 'docs/_templates'
  Installing collected packages: virtualenv
  Running setup.py install for virtualenv
  
  warning: no previously-included files matching '*.*' found under directory 'docs/_templates'
  Installing virtualenv script to /usr/local/bin
  Successfully installed virtualenv
  Cleaning up...
  
  
  $ python virtualenv.py ENV
  /Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/‌​MacOS/Python: can't open file 'virtualenv.py': [Errno 2] No such file or directory
  </code></pre>
  
  <p>The virtualenv.py is located at /Library/Python/2.7/site-packages/virtualenv.py and /System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/py2app/recipes/virtualenv.py but somehow python misses all. </p>
  
  <p>Why there is so much mess? How should I proceed to fix this?</p>