What's our minimum supported Python version?

Our fine manual claims the answer to $SUBJECT is 3.2.

However, there is room to doubt that our code still actually
works with 3.2, because the oldest version I can find being
tested by the buildfarm is topminnow's 3.4.2. The next oldest
is shelduck's 3.4.10, and everything else has 3.5.2 or newer.
topminnow hasn't reported in a couple months, so it may
actually be dead.

The reason I bring this up is that I found out the hard way
that src/test/modules/oauth_validator fails on RHEL8, because
its oauth_server.py script is not compatible with the 3.6.8
version of Python supplied by this distro. (There are 22
buildfarm animals running 3.6.8, presumably mostly also Red
Hat-derived platforms, so I'm not going to apologize for
my workstation being a little long in the tooth.)

I think we need to do some combination of moving our
minimum-supported-version goalposts forward, making sure that
whatever we claim is the minimum Python version is actually
being tested in the buildfarm, and fixing oauth_server.py
so that it works on that version.

I am not familiar enough with the Python landscape to
have an informed opinion about what the minimum supported
version should be. But I'll present this data scraped
from the buildfarm about how many animals are running what
(counting animals that have reported since 2025-01-01):

Count Version

1 3.4.2
1 3.4.10
2 3.5.2
3 3.5.3
2 3.6.5
22 3.6.8
3 3.6.9
5 3.6.15
1 3.7.1
2 3.7.3
1 3.7.10
2 3.7.16
1 3.8.8
4 3.8.10
15 3.9.2
6 3.9.16
6 3.9.18
1 3.9.19
2 3.9.20
13 3.9.21
6 3.10.x
18 3.11.x
21 3.12.x
22 3.13.x

160 total

Thoughts?

regards, tom lane