> Remember that we had the hardcoded 2.7 without it installing the Homebrew Python in depends_on :python for a (relatively) long time with no complaints

`depends_on :python` creates a hard dep on Python 2.7, it just allows it to alternately be satisfied by the Homebrew Python if the system one isn't compatible. For instance, trying to `brew install ansible` now will introduce a dependency on the Homebrew Python if the system Python is too old, but will accept the system Python otherwise. That's why we've had no complaints - it works transparently.