gh-133319: Use python versioning in msgfmt & pygettext

[StanFromIreland]

Simplest approach maintaining full backwards compatibility. We cannot use the version of the python running the script, updating this number every few years is not overly complex, it can be picked up by any pr modifying the file.

• Issue: Use Python versioning in msgfmt.py/pygettext.py #133319

[StanFromIreland]

Request: @tomasr8 , @serhiy-storchaka

[encukou]

This would put the burden of updating the numbers on the release manager, who bumps the CPython version. I doubt they'll want that.

Can you find a way to do this with less maintenance overhead?

[StanFromIreland]

IMO it shouldn’t fall on the release manager, since the file won’t have changed anyway. In my mind I think it should just be done as part of whatever pr that modifies the script in a given version.

Using the version of the python running it will be misleading.

[encukou]

Ah. Could you document that expectation; perhaps put the command to do it in a comment?

[StanFromIreland]

perhaps put the command to do it in a comment?

I can do that.

[encukou]

Sorry, I assumed the discussion is further along.
First let's clarify what the versioning scheme should be; see discussion on the issue. After that, it'll be time to implement it.