title: What's causing this error when I try and install virtualenv? IOError: [Errno 13] Permission denied: '/Library/Python/2.7/site-packages/virtualenv.py'
body: <p>I'm trying to install a virtual environment using the command:</p>
  
  <p><code>pip install virtualenv</code></p>
  
  <p>but I get the following error:</p>
  
  <p><code>IOError: [Errno 13] Permission denied: '/Library/Python/2.7/site-packages/virtualenv.py'</code></p>
  
  <p>How do I fix this?</p>