title: What is the -H flag for pip?
body: <p>When using <code>sudo pip install ...</code> with pip version 6.0.4 or greater, I get some warnings like:</p>
  
  <blockquote>
    <p>The directory '/home/drevicko/.cache/pip/log' or its parent directory is not owned by the current user and the debug log has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want the -H flag.</p>
  </blockquote>
  
  <p>This warning appears to have been <a href="http://pip.readthedocs.org/en/latest/news.html">added in 6.0.4</a>, but the <code>-H</code> flag doesn't appear in the <a href="http://pip.readthedocs.org/en/latest/reference/pip_install.html#options"><code>pip install</code> docs</a> nor in the docs on <a href="http://pip.readthedocs.org/en/latest/reference/pip.html#general-options">pip's general options</a>.</p>
  
  <p>So, what is the <code>-H</code> flag and why do I need it when using <code>sudo pip install ...</code>?</p>