Since ENV filtering became the default this has been chucking
erroneous warnings from both `brew doctor` and things like `brew install pygobject`
about needing to run:
```
echo 'import site; site.addsitedir("/usr/local/lib/python2.7/site-packages")' >> /Users/xyz/Library/Python/2.7/lib/python/site-packages/homebrew.pth
```
even though I had Homebrew's `python` installed.
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.