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.
d6ebdf1e62