On Jun 16, 2017, at 5:01 PM, Nathaniel Smith <njs@pobox.com> wrote:
If someone wants to experiment with this, then it's possible within the PEP 517 framework to write a 2.7-compatible backend that searches the system for a python 3 install and then uses it. I'm not sure it's a good idea, but you can do it :-).
I just want to hammer this specific point home a bit more. The only real requirement on Python version PEP 517 puts into place is that you write the API that the frontend will call in the version of Python the frontend is running under. What you do beyond that is entirely up to you, including running a different version of Python or something that’s not written in Python at all. The only “downside" to this really is that your options if that build system isn’t available is to have some sort of fallback (in which case why have the other thing at all?) or just error out. However I don’t think this is a solvable downside, because in either case if you’re running on py3 and the build backend needs py2, there’s nothing really for a frontend to do here except bail out. — Donald Stufft