title: pip install -U mock : Error
body: <p>I am trying to install mock for unit test a class in Python. I used the following command on terminal to install mock:</p>
  
  <pre><code>$ sudo pip install -U mock
  </code></pre>
  
  <p>I am getting the following error:</p>
  
  <pre><code>OSError: [Errno 1] Operation not permitted: '/tmp/pip-4u8kWt-uninstall/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/six-1.4.1-py2.7.egg-info'
  </code></pre>
  
  <p>I am refererring to this in order to learn mocking for Python unit testing: <a href="https://myadventuresincoding.wordpress.com/category/python/" rel="nofollow">https://myadventuresincoding.wordpress.com/category/python/</a></p>
  
  <p>I have Python 2.7.10 installed.</p>
  
  <p>How can I resolve this error?</p>