pypa/pip — pull request #880 by dholth (2013-04-01 17:37:10+00:00)
Title: wheel errors if distribute >= 0.6.34 not installed

a little tricky to test this and make sure it catches all the right places, since I'm not sure there is a single entry point for "we are trying to use wheel now" that catches it before one might be downloaded only to be un-installable due to dependencies.