title: Combine --user with --prefix error with setup.py install
body: <p>I was trying to install Python packages a system I recently gained access to. I was trying to take advantage of Python's relatively new <a href="http://docs.python.org/whatsnew/2.6.html#pep-370-per-user-site-packages-directory" rel="noreferrer">per user site-packages directory</a>, and the new option <code>--user</code>. (The option is <a href="http://bugs.python.org/issue10745" rel="noreferrer">currently undocumented</a>, however it exists for Python 2.6+; you can see the help by running <code>python setup.py install --help</code>.)</p>
  
  <p>When I tried running</p>
  
  <pre><code>python setup.py install --user
  </code></pre>
  
  <p>on any package I downloaded, I always got the following error:</p>
  
  <pre><code>error: can't combine user with with prefix/exec_prefix/home or install_(plat)base
  </code></pre>
  
  <p>The error was extremely perplexing because, as you can see, I wasn't providing the <code>--prefix</code>, <code>--exec-prefix</code>, <code>--install-base</code>, or <code>--install-platbase</code> flags as command line options. I wasted a lot of time trying to figure out what the problem was. I document my answer below, in hopes to spare some other poor soul a few hours of <a href="http://en.wiktionary.org/wiki/yak_shaving" rel="noreferrer">yak shaving</a>.</p>