Upgrade Pip error message
<p>When i run </p>

<pre><code>    pip install --upgrade pip
</code></pre>

<p>I get this error message:</p>

<pre><code>    Collecting pip
    Downloading pip-8.1.0-py2.py3-none-any.whl (1.2MB)
    100% |████████████████████████████████| 1.2MB 371kB/s 
    Installing collected packages: pip
    Found existing installation: pip 8.0.2
    Uninstalling pip-8.0.2:
    Exception:
    Traceback (most recent call last):
    File "/Library/Python/2.7/site-packages/pip/basecommand.py", line       209, in main
    status = self.run(options, args)
    File "/Library/Python/2.7/site-packages/pip/commands/install.py", line 317, in run
    prefix=options.prefix_path,
    File "/Library/Python/2.7/site-packages/pip/req/req_set.py", line  725, in install
    requirement.uninstall(auto_confirm=True)
    File "/Library/Python/2.7/site-packages/pip/req/req_install.py", line 752, in uninstall
    paths_to_remove.remove(auto_confirm)
    File "/Library/Python/2.7/site-packages/pip/req/req_uninstall.py",line 115, in remove
    renames(path, new_path)
    File "/Library/Python/2.7/site-packages/pip/utils/__init__.py", line 266,   in renames
    shutil.move(old, new)
    File"/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 303, in move
    os.unlink(src)
    OSError: [Errno 13] Permission denied: '/Library/Python/2.7/site- packages/pip-8.0.2.dist-info/DESCRIPTION.rst'
</code></pre>

<p>Previously I had been struggling to install and run a couple of python modules so I remember moving files around a bit. Is that what has caused this error? How can I fix this? I am on Mac. </p>

<p>I was trying to install bs4 prior to this and I got similar error messages. (But i suspect the bs4 install has more issues so that's another question for later). </p>

<p>Also sorry for any format issues with the code. Have tried my best to make it look like it is on the terminal.</p>

<p>Thanks.</p>