title: Can't upgrade my version of pip. Something is wrong with my setup
body: <p>I was trying to install something using pip, and I keep getting this UserWarning error (see below).</p>
  
  <p>I tried to upgrade pip and you can see the error below.</p>
  
  <p>I haven't used python on my system in a while and it seems to be broken.  What could it be?</p>
  
  <pre><code>pip install -U pip
  /usr/local/bin/pip:5: UserWarning: Module _markerlib was already imported from /Library/Python/2.7/site-packages/distribute-0.6.49-py2.7.egg/_markerlib/__init__.pyc, but /System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python is being added to sys.path
    from pkg_resources import load_entry_point
  Downloading/unpacking pip from https://pypi.python.org/packages/py2.py3/p/pip/pip-7.1.2-py2.py3-none-any.whl#md5=5ff9fec0be479e4e36df467556deed4d
    Downloading pip-7.1.2-py2.py3-none-any.whl (1.1MB): 1.1MB downloaded
  Installing collected packages: pip
    Found existing installation: pip 1.5.6
      Uninstalling pip:
  Cleaning up...
  Exception:
  Traceback (most recent call last):
    File "/Library/Python/2.7/site-packages/pip/basecommand.py", line 122, in main
      status = self.run(options, args)
    File "/Library/Python/2.7/site-packages/pip/commands/install.py", line 283, in run
      requirement_set.install(install_options, global_options, root=options.root_path)
    File "/Library/Python/2.7/site-packages/pip/req.py", line 1431, in install
      requirement.uninstall(auto_confirm=True)
    File "/Library/Python/2.7/site-packages/pip/req.py", line 598, in uninstall
      paths_to_remove.remove(auto_confirm)
    File "/Library/Python/2.7/site-packages/pip/req.py", line 1836, in remove
      renames(path, new_path)
    File "/Library/Python/2.7/site-packages/pip/util.py", line 295, in renames
      shutil.move(old, new)
    File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 302, in move
      os.unlink(src)
  OSError: [Errno 13] Permission denied: '/Library/Python/2.7/site-packages/pip-1.5.6.dist-info/DESCRIPTION.rst'
  
  Storing debug log for failure in /Users/blankman/Library/Logs/pip.log
  </code></pre>