chore(python): add Python 3.12 in test matrix

[stegayet]

Summary of changes

Closes #1301.

Pull Request Checklist

• Changes have tests
• Authors have been added to AUTHORS.md
• News fragment added in changelog.d. See CONTRIBUTING.md for details

[stegayet]

I seems this work is already ongoing in #1290.

[hugovk]

@stegayet This PR has more of the necessary parts than #1290.

I recommend adding this, it will allow the 3.12 jobs to run, regardless of the unrelated 2.7 failures:

diff --git a/.github/workflows/validate.yml b/.github/workflows/validate.yml
index b02427c..4e68c0a 100644
--- a/.github/workflows/validate.yml
+++ b/.github/workflows/validate.yml
@@ -11,6 +11,7 @@ on:
 jobs:
   test:
     strategy:
+      fail-fast: false
       matrix:
         python-version: [
           "2.7",

[cbrnr]

Python 2.7 has been removed from the runners on June 19. There are two options:

1. Remove tests on Python 2.7
2. Create custom solution to continue running tests on Python 2.7

Since Python 2.7 is EOL since 2020, I'd recommend the first option.

[hugovk]

I agree but let's not discuss Python 2.7 here, instead please see #653 and #1291. The failing 2.7 CI job need not delay this PR.

[cbrnr]

All other jobs are green, is there anything else that's missing?

[ThomasWaldmann]

LGTM! Would be good to merge this.

Python 3.12 with dateutil 2.8.2 shows a deprecation warning:

.tox/py312-fuse3/lib/python3.12/site-packages/dateutil/tz/tz.py:37: 16 warnings
/vagrant/borg/borg/.tox/py312-fuse3/lib/python3.12/site-packages/dateutil/tz/tz.py:37: DeprecationWarning: datetime.datetime.utcfromtimestamp() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.fromtimestamp(timestamp, datetime.UTC).
     EPOCH = datetime.datetime.utcfromtimestamp(0)

BTW, the setuptools_scm related failure seen in the test run might go away with 8.0.4.

[cclauss]

Please rebase so we can see if the tests now pass.