title: Python2.7: ImportError: six 1.3 or later is required; you have 1.2.0
body: <p>Got this error when importing matplotlib.pyplot. But I have checked the version of six installed using <code>pip list</code>, and it returns version 1.9.0. And when I checked <code>six.__version__</code>, it returns 1.2.0.</p>
  
  <p>Could any one help me?</p>