title: Python: pip tries to install to /bin directory
body: <p>I installed python with <code>brew install python</code></p>
  
  <pre><code>which pip
  /usr/local/bin/pip
  </code></pre>
  
  <p>my <code>PYTHONPATH</code> shows <code>/usr/local/lib/python2.7/site-packages/</code></p>
  
  <p>However, when I try to install something with pip, it goes to the <code>/bin/</code> directory as shown below. I want things installed to <code>/usr/local/lib/python2.7/site-packages/</code>. How do I fix this? </p>
  
  <pre><code>pip install virtualenv
  Downloading/unpacking virtualenv
    Downloading virtualenv-1.11.6-py2.py3-none-any.whl (1.6MB): 1.6MB downloaded
  Installing collected packages: virtualenv
  Cleaning up...
  Exception:
  Traceback (most recent call last):
    File "/usr/local/lib/python2.7/site-packages/pip-1.5.6-py2.7.egg/pip/basecommand.py", line 122, in main
      status = self.run(options, args)
    File "/usr/local/lib/python2.7/site-packages/pip-1.5.6-py2.7.egg/pip/commands/install.py", line 283, in run
  {....}
    File "/usr/local/lib/python2.7/site-packages/pip-1.5.6-py2.7.egg/pip/_vendor/distlib/util.py", line 384, in write_binary_file
      with open(path, 'wb') as f:
  IOError: [Errno 13] Permission denied: '/bin/virtualenv'
  
  
  
  $ pip list
  pip (1.5.6)
  setuptools (5.4.2)
  wsgiref (0.1.2)
  
  
  $pip show setuptools
  ---
  Name: setuptools
  Version: 5.4.2
  Location: /usr/local/lib/python2.7/site-packages/setuptools-5.4.2-py2.7.egg
  Requires:
  </code></pre>
  
  <p>So pip already has the basic packages installed to site-packages. However, running the same exact pip to install virtualenv tries to install to /bin/. </p>