title: ubuntu python pip can't uninstall pillow
body: <p>When I try to uninstall pillow using pip ,it outputs:</p>
  
  <pre><code>qixin@qixin:~$ pip uninstall pillow
  Uninstalling Pillow:
    /usr/local/bin/pilconvert.py
    ......
    /usr/local/lib/python2.7/dist-packages/Pillow-2.7.0.egg-info
  Proceed (y/n)? y
  Exception:
  Traceback (most recent call last):
    File "/usr/local/lib/python2.7/dist-packages/pip-1.5.4-py2.7.egg/pip/basecommand.py", line 122, in main
      status = self.run(options, args)
    File "/usr/local/lib/python2.7/dist-packages/pip-1.5.4-py2.7.egg/pip/commands/uninstall.py", line 59, in run
      requirement_set.uninstall(auto_confirm=options.yes)
    File "/usr/local/lib/python2.7/dist-packages/pip-1.5.4-py2.7.egg/pip/req.py", line 1035, in uninstall
      req.uninstall(auto_confirm=auto_confirm)
    File "/usr/local/lib/python2.7/dist-packages/pip-1.5.4-py2.7.egg/pip/req.py", line 598, in uninstall
      paths_to_remove.remove(auto_confirm)
    File "/usr/local/lib/python2.7/dist-packages/pip-1.5.4-py2.7.egg/pip/req.py", line 1836, in remove
      renames(path, new_path)
    File "/usr/local/lib/python2.7/dist-packages/pip-1.5.4-py2.7.egg/pip/util.py", line 295, in renames
      shutil.move(old, new)
    File "/usr/lib/python2.7/shutil.py", line 303, in move
      os.unlink(src)
  OSError: [Errno 13] Permission denied: '/usr/local/bin/pilconvert.py'
  
  Storing debug log for failure in /tmp/tmpEmRbAF
  </code></pre>
  
  <p>My OS is ubuntu 14.04,python's version is 2.7.
  Why did it fail? Thanks much!</p>