Magic Lantern development compiler.app (Mac OS)

[Danne]

You can uninstall python 3 and it should jump into python 2.

[names_are_hard]

I guess so, but:
 - presumably they have Python 3 installed for a reason, installing Xcode can install Python 3 so uninstalling may be impractical
 - Python 2 is EOL and out of support so some path that moves away from it is preferred
 - Apple have stated future versions of OSX will not have Python 2

Might still be a good workaround for now.

[TequilaKez]

Ok I'm in business!

So I think yes that's crux of it. It seems, at least on 10.13.6 anyway, macOS has python2.7 installed under python, but thats it.
Brew has installed other python versions on my system at some stage, but 'which python2' gives me nothing so its going nowhere.

So it was as easy as installing python2 via brew, although I had to do it from a commit as python@2 didn't want to work.

For anyone following, this commit did the trick

brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/86a44a0a552c673a05f11018459c9f5faae3becc/Formula/python@2.rb

Thanks for the help!

[names_are_hard]

Cool!  Apple really doesn't seem to like following standards!