Update test_validators.py for Python 3.15a7

[vstinner]

matches_re() error message changed in Python 3.15 alpha 7 with the introduction of re.prefixmatch().

Summary

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    The next version is the second number in the current release + 1.
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[vstinner]

• re.prefixmatch() change: gh-86519: Add prefixmatch APIs to the re module python/cpython#31137
• Downstream Fedora issue: https://bugzilla.redhat.com/show_bug.cgi?id=2447915

[vstinner]

It's possible to keep support for Python 3.15 alpha 6 by checking the whole version:

Suggested change

	if sys.version_info >= (3, 15):
	if sys.version_info >= (3, 15, 0, 'alpha', 7):

I don't think that it's worth it to support older alpha versions, so I just wrote (3, 15).

[hynek]

yeah for us there's only the next big release, so this is correct

[vstinner]

Changes have news fragments in changelog.d.

Python 3.15 is not released yet (it's still an alpha version), so I didn't add a changelog fragment.

[hynek]

thanks!

[hynek]

@vstinner are y'all already testing 3.15 at RH? Can we expect more big things or is it a chiller release than 3.14?

[hroncok]

are y'all already testing 3.15 at RH?

As always, since 3.15.0a1 :) https://status.fedoralovespython.org/

Can we expect more big things or is it a chiller release than 3.14?

Usually, it's the first beta where all the changes are rushed in for the last possible moment, that decides this :D

[vstinner]

Thanks for (very) quickly merging my fix!

@vstinner are y'all already testing 3.15 at RH?

Yes, we are rebuilding all Python packages with the latest Python 3.15 release (so 3.15a7 currently), and most Python Fedora packages are running their test suite as part of the package build process. That's how we discovered the attrs issue on alpha7.

Can we expect more big things or is it a chiller release than 3.14?

That's the funny part: we don't know in advance :-D Things should settle down in May with the feature freeze (Python 3.15 beta1). My own opinion is that 3.15 migration seems to be easier than the 3.14 migration: less breaking changes.