Pin python <3.12 for 2.10 release

[valeriupredoi]

see eg all manners of failed flake8 tests - python=3.12 seems to be bringing in massive PITAs - and, more importantly, conda-lock found a solution for the environment to build which means two things:

• I must revisit our attempt to support python=3.12 in Add support for Python=3.12 #2228
• it looks like it's still not 100% ready for python=3.12 support, but an env solution sneaked through, so we should probably pin to < 3.12 in the release and package build on feedstock -> @zklaus

[valeriupredoi]

indeed python 3.12 environment now builds without any incantations https://github.com/ESMValGroup/ESMValCore/actions/runs/6708774145/job/18230325803?pr=2228 but we are running into these flake8 distaters, I think we need to pin < 3.12 asap

[bouweandela]

It looks like it's just a few code formatting issues, those should be easy enough to fix and as far as I can see they will not affect the proper functioning of the tool.

[valeriupredoi]

indeed! I too am for allowing Python 3.12 to trick-or-treat us, but there may be other issues that'll pop up - that's why I am leaving this to the RM and RMXO to decide - @zklaus and you 😁 (RMXO - release manager executive officer)

[zklaus]

Actually, the alleged Flake8 violations seem to stem from Flake8 now checking the contents of f-strings, e.g. missing space after : in f'http://something.org/ABC/v1/{filename}'. So I think that is a Flake8 bug, possibly induced by a grammar change in Python 3.12. I looked a bit and couldn't find an issue on the Flake8 issue tracker, but perhaps we'll have to wait and see?

[valeriupredoi]

saw this was enforced by Flake8 as something valid, folks, it's on their list of no-no's (my way of calling it since I forgot the actual standard's code). I am thinking, if we allow 3.12 in Core, we'll prob have some issues in Tool - do we want to do that and fix anything that may go belly-up in Tool, while we're doing the release? If so, I can work on this today, see if anything's broken in Tool with 3.12-Core

[zklaus]

Could you point us to where they say that?

[valeriupredoi]

shall dig it out in a jiffy, bud

[valeriupredoi]

here is the E231 gents - it does, however, look like a fairly old rule, and I don't know why it's decided to wake up only now for 3.12

[valeriupredoi]

there is also E713 test for membership should be 'not in' which I agree with, but again, decided to wake up only now, and a couple more different ones - I reckon we can just turn off flake8 temporarily and wait see how they handle all this, for now; and still get 3.12 in - opinions?