[do not merge] ref: Remove residual Python 2 compatibility code

[ericapisani]

Summary

Python 2 support was dropped in SDK 2.0.0, but a handful of Python 2 shims, unreachable branches, and stale py2 comments lingered. This PR cleans them up. No behavior change.

• Delete with_metaclass() from sentry_sdk/_compat.py and rewrite class Hub(with_metaclass(HubMeta)) to use the native metaclass= keyword (drops a # type: ignore).
• Remove the im_class/im_func try/except in qualname_from_function (unreachable on Python 3) and collapse the __qualname__ vs __name__ elif in utils.qualname_from_function and Django signals_handlers._get_receiver_name.
• Drop the try: ModuleNotFoundError except Exception: ImportError shim in client.py and use ModuleNotFoundError directly. ModuleNotFoundError is available in all supported Python versions (3.6+).
• Replace super(_Client, self).__init__(...) with super().__init__(...).
• Remove the bdist_wheel universal=1 option from setup.py; universal wheels are Py2/Py3-compat only.
• Strip misleading Py2 references from comments in the Django middleware integration and tests/conftest.py.

Minimum supported Python stays at 3.6 — Python 3.6-vs-later compat (e.g. aiocontextvars, nullcontext, re.Pattern fallback, BaseExceptionGroup try/except) is intentionally left untouched.

Test plan

• tox -e ruff passes
• tox -e mypy passes (removing with_metaclass lets us drop the # type: ignore on Hub)
• tox -e py3.14-common — 2114 passed, 154 skipped
• Smoke test: Hub.current / Hub.main properties still dispatch via the HubMeta metaclass; qualname_from_function still resolves functions, methods, lambdas, and partials
• CI green on all matrix environments

🤖 Generated with Claude Code

[github-actions]

Semver Impact of This PR

⚪ None (no version bump detected)

📋 Changelog Preview

This is how your changes will appear in the changelog.
Entries from this PR are highlighted with a left border (blockquote style).

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New Features ✨

• (ci) Cancel in-progress PR workflows on new commit push by joshuarli in #5994
• Add db.driver.name spans to database integrations by ericapisani in #6082

Bug Fixes 🐛

• (google_genai) Redact binary data in inline_data and fix multi-part message extraction by ericapisani in #5977
• (grpc) Add isolation_scope to async server interceptor by robinvd in #5940
• (profiler) Stop nulling buffer on teardown by ericapisani in #6075

Internal Changes 🔧

• (celery) Remove unused NoOpMgr from utils by sentrivana in #6078
• (ci) Update outdated pinned action version comments by JoshuaMoelans in #6088
• (pydantic-ai) Remove dead Model.request patch by alexander-alderman-webb in #5956
• (tests) Replace deprecated enable_tracingwith traces_sample_rate by sentrivana in #6077
• Set explicit base-branch for codecov action by ericapisani in #5992

Other

• [do not merge] ref: Remove residual Python 2 compatibility code by ericapisani in #6091

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_{🤖 This preview updates automatically when you update the PR.}

[github-actions]

Codecov Results 📊

✅ 142 passed | Total: 142 | Pass Rate: 100% | Execution Time: 20.99s

All tests are passing successfully.

❌ Patch coverage is 37.50%. Project has 14134 uncovered lines.

Files with missing lines (9)

File	Patch %	Lines
utils.py	52.05%	⚠️ 444 Missing and 81 partials
client.py	53.75%	⚠️ 247 Missing and 60 partials
traces.py	36.07%	⚠️ 195 Missing
tracing.py	70.83%	⚠️ 140 Missing and 49 partials
hub.py	45.31%	⚠️ 105 Missing and 3 partials
middleware.py	0.00%	⚠️ 90 Missing
views.py	0.00%	⚠️ 47 Missing
signals_handlers.py	0.00%	⚠️ 42 Missing
_compat.py	30.30%	⚠️ 23 Missing

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Generated by Codecov Action

[github-actions]

Codecov Results 📊

✅ 49 passed | ⏭️ 3 skipped | Total: 52 | Pass Rate: 94.23% | Execution Time: 12.12s

📊 Comparison with Base Branch

Metric	Change
Total Tests	📉 -49
Passed Tests	📉 -51
Failed Tests	—
Skipped Tests	📈 +2

All tests are passing successfully.

❌ Patch coverage is 66.67%. Project has 15661 uncovered lines.
❌ Project coverage is 26.63%. Comparing base (base) to head (head).

Files with missing lines (6)

File	Patch %	Lines
utils.py	50.76%	⚠️ 456 Missing and 80 partials
client.py	53.18%	⚠️ 250 Missing and 62 partials
hub.py	45.31%	⚠️ 105 Missing and 3 partials
middleware.py	0.00%	⚠️ 90 Missing
signals_handlers.py	0.00%	⚠️ 42 Missing
_compat.py	30.30%	⚠️ 23 Missing

Coverage diff

@@            Coverage Diff             @@
##          main       #PR       +/-##
==========================================
- Coverage    31.19%    26.63%    -4.56%
==========================================
  Files          190       190         —
  Lines        21365     21346       -19
  Branches      7068      7064        -4
==========================================
+ Hits          6663      5685      -978
- Misses       14702     15661      +959
- Partials       540       490       -50

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Generated by Codecov Action