Amends e4d0187120e61bc80d31ebecc3b38f0740b20bb5. The `require` was
accidentally omitted causing the tests to fail very sporadically (or
always, when invoked as `brew tests --only=integration_cmds`).
This is the (partially) documented public API for Homebrew.
The main class you should look at is the {Formula} class (and classes linked from there). That's the class that's used to create Homebrew formulae (i.e. package descriptions). Assume anything else you stumble upon is private.