title: Unusual error while installing any pip based package
body: <p>I do not remember since when, but whenever I install any <code>pip</code> based package, my system (Ubuntu 14.04, Python 2.7.6) trows a warning/error :</p>
  
  <pre><code>Url 'file:///home/username/.pip-wheelhouse' is ignored: it is neither a file nor a directory.
  </code></pre>
  
  <p>I don't know where this line came from but the pip package I'm installing installs very well, but this line is always shown. How can I remove this ?</p>