What do you propose set to in Windows? There is no `python2.exe` installed with `Python2.7`, nor is there a standard system PATH where we can expect a `python2`. Perhaps we can simply `process.exit()` if we find `python.exe --version`'s output doesn't match `^Python 2.7`?

Yes, I initially used `!...`; I hadn't read the style guide and simply assumed explicit was preferred to implicit. I'll change it.