Re: Python versions (was Re: RHEL 8.0 build)

Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> writes:
> On 28/11/2018 22:41, Tom Lane wrote:
>> Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> writes:
>>> My suggestion is to either
>>> - Change the probe order to python, python3 in master, or
>>> - Don't change anything until PEP 394 is updated.

>> It's hard to evaluate the latter unless we have some idea how soon
>> that update is likely to happen ... have you heard any little birdies
>> chattering about that lately?

> No, I haven't heard anything. I would be slightly surprised if anything
> changed there before PG12 is released.

Yeah, I think your option 2 is effectively the same as "do nothing".

After sleeping on it for awhile, I am liking the idea of probing
python, python3, python2 (while keeping the $PYTHON override of
course). This continues to work as before for any case that
worked before, ie when you either have "python" or used $PYTHON.
It also works for cases where you have only "python3" or only
"python2", which per this thread are becoming more common.
If you have both, then we're stuck with either making an
arbitrary choice or failing. Your proposal at the top is to
arbitrarily choose "python3", which I'm okay with. But if we're
touching this at all, I don't see a good excuse for failing
when the only thing we can find is "python2". The user's intent
seems pretty clear in that case.

Also, I think it'd be fine to back-patch such a change, again
on the grounds that it isn't breaking any case that worked before,
and people are likely to wish to use already-released branches
on platforms that stopped supplying "python".

regards, tom lane