title: python, change user site directory or install setup.py --prefix with --user
body: <p>I'd want to install python modules as non-root user like this</p>
  
  <pre><code>$ pip install -I --install-option="--prefix=~/usr" scipy
  </code></pre>
  
  <p>Unfortunately this usually does not work unless you specify <code>--user</code>. But <code>--user</code> can't be used together with <code>--prefix</code>. Using <code>--user</code> only (without <code>--prefix</code>) installs to <code>~/.local</code> which I find ugly because I have a well maintained <code>~/usr</code> and don't want to add even more stuff to my <code>env</code> to make <code>~/.local</code> usable too.</p>
  
  <p>So my questions:</p>
  
  <ol>
  <li>How can I let <code>--prefix</code> and <code>--user</code> work together for setup.py or how else could setup.py succeed without using <code>--user</code>?</li>
  <li>Or can I change the user site directory from <code>~/.local</code> to <code>~/usr</code> somehow by <code>env</code>?</li>
  </ol>