title: virtualenv's python can't find PyQt4
body: <p>Running OSX (10.8.2) here, replaced their python with Homebrew's.  All good:</p>
  
  <p><code>$ which python
  /usr/local/bin/python</code></p>
  
  <p>Installed pip, virtualenv with brew python.  Installed pyqt with brew. </p>
  
  <p>If I </p>
  
  <pre><code>$ python
  &gt;&gt;&gt; import PyQt4
  </code></pre>
  
  <p>, no problems.  However, if I </p>
  
  <pre><code>(env)$ python
  &gt;&gt;&gt; import PyQt4
  Traceback (most recent call last):
  File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  ImportError: No module named PyQt4
  </code></pre>
  
  <p>Why can't the virtualenv python environment see my system-wide install of pyqt?</p>
  
  <p>Thanks!</p>