title: how to create virtualenv with pypy?
body: <p>running the following command</p>
  
  <pre><code>virtualenv -p /usr/local/bin/pypy pypy
  </code></pre>
  
  <p>exits with error like</p>
  
  <pre><code>Running virtualenv with interpreter /usr/local/bin/pypy
  New pypy executable in pypy/bin/pypy
  debug: WARNING: Library path not found, using compiled-in sys.path.
  debug: WARNING: 'sys.prefix' will not be set.
  debug: WARNING: Make sure the pypy binary is kept inside its tree of files.
  debug: WARNING: It is ok to create a symlink to it from somewhere else.
  'import site' failed
  AttributeError: 'module' object has no attribute 'prefix'
  ERROR: The executable pypy/bin/pypy is not functioning
  ERROR: It thinks sys.prefix is u'/Users/myname' (should be u'/Users/myname/pypy')
  ERROR: virtualenv is not compatible with this system or executable
  </code></pre>
  
  <p>I'm running Mac OS X 10.8.1 (Mountain Lion) with CPython 2.7.3 and installed pypy 1.9 using Brew. virtualenv's version is 1.8.4</p>
  
  <p>Using pre-built pypy binary for Mac OS X downloaded directly from pypy's website doesn't make any difference</p>