title: pip install fails with /usr/bin/clang: No such file or directory
body: <p>I am migrating my dev environment to 10.8, however I am having issues with pip.</p>
  
  <p>Specifically, I'm using a virtualenvs/virtualwrapper but cannot <code>pip install psycopg2</code>, and during the building of the <code>psycopg2._psycopg</code> extension, I get:</p>
  
  <pre><code>unable to execute /usr/bin/clang: No such file or directory
  error: command '/usr/bin/clang' failed with exit status 1
  </code></pre>
  
  <p>Can anyone offer a solution to this?</p>