mxcl/homebrew — pull request #19474 by telemachus (2013-04-27 19:41:38+00:00)
Title: Prevent `brew versions` from erroring on success

At the end of a successful run, `brew versions` will sometimes still print
an error (see #18565). Raising a specific exception in Formula and catching
it in the versions command fixes the problem.

See my discussion with @adamv starting [here](https://github.com/mxcl/homebrew/issues/18565#issuecomment-17120315).