Drop 3.9 support + add 3.14 CI

[cooperlees]

• Update pyproject.toml etc.
• Add to CI runs
• Drop 3.9 as flake8 itself did

Test:

• Run tox in 3.14
  • python3 -m venv /tmp/tf --upgrade-deps
  • /tmp/tf/bin/pip install tox
  • /tmp/tf/bin/tox -e py314

[Copilot]

Pull Request Overview

This PR drops support for Python 3.9 and adds Python 3.14 to the CI pipeline, aligning with flake8's supported versions.

• Removed Python 3.9 from all configuration files and CI workflows
• Added Python 3.14 support to tox, pyproject.toml, and CI
• Updated documentation to reflect the new minimum Python version (3.10)

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tox.ini	Removed py39 from envlist and gh-actions mapping; added py314 support
pyproject.toml	Updated Python version classifiers and minimum required version to 3.10
DEVELOPMENT.md	Updated documentation to reflect Python 3.10 as the new minimum version
.github/workflows/flake8_py_version_check.yml	Removed hardcoded Python 3.12 version to allow flexibility
.github/workflows/ci.yml	Updated CI matrix to test Python 3.10-3.14 instead of 3.9-3.13

Comments suppressed due to low confidence (1)

tox.ini:4

• The envlist still includes py39 but Python 3.9 support has been dropped. Remove py39 from this list to match the gh-actions configuration and project requirements.

envlist = py39, py310, py311, py312, py313, pep8_naming, mypy

---

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[Copilot]

The documentation states tests run on Python 3.10 through 3.13, but Python 3.14 support has been added. Update to '3.10 through 3.14' to reflect the current configuration.

Suggested change

	will by default run all tests on python versions 3.10 through 3.13. If you only want to test a specific version you can specify the environment with `-e`
	will by default run all tests on python versions 3.10 through 3.14. If you only want to test a specific version you can specify the environment with `-e`

[cooperlees]

@kasium - This makes sense right?

[kasium]

yes, seems like a mistake I did

[cooperlees]

Seems we have new warnings to fix too:

tests/test_bugbear.py::test_eval[B012]
  <unknown>:5: SyntaxWarning: 'return' in a 'finally' block

tests/test_bugbear.py::test_eval[B012]
  <unknown>:13: SyntaxWarning: 'return' in a 'finally' block

tests/test_bugbear.py::test_eval[B012]
  <unknown>:21: SyntaxWarning: 'return' in a 'finally' block

tests/test_bugbear.py::test_eval[B012]
  <unknown>:31: SyntaxWarning: 'return' in a 'finally' block

tests/test_bugbear.py::test_eval[B012]
  <unknown>:44: SyntaxWarning: 'return' in a 'finally' block

tests/test_bugbear.py::test_eval[B012]
  <unknown>:66: SyntaxWarning: 'break' in a 'finally' block

tests/test_bugbear.py::test_eval[B012]
  <unknown>:78: SyntaxWarning: 'continue' in a 'finally' block

tests/test_bugbear.py::test_eval[B012]
  <unknown>:101: SyntaxWarning: 'continue' in a 'finally' block

tests/test_bugbear.py::test_eval[B012]
  <unknown>:107: SyntaxWarning: 'break' in a 'finally' block

tests/test_bugbear.py::test_eval[B012_PY311]
  <unknown>:7: SyntaxWarning: 'return' in a 'finally' block

tests/test_bugbear.py::test_eval[B012_PY311]
  <unknown>:17: SyntaxWarning: 'return' in a 'finally' block

tests/test_bugbear.py::test_eval[B012_PY311]
  <unknown>:27: SyntaxWarning: 'return' in a 'finally' block

diff --git a/tests/test_bugbear.py b/tests/test_bugbear.py
index 04835cf..1e34616 100644
--- a/tests/test_bugbear.py
+++ b/tests/test_bugbear.py
@@ -8,6 +8,7 @@ import site
 import subprocess
 import sys
 import unittest
+import warnings
 from argparse import Namespace
 from pathlib import Path

@@ -54,7 +55,12 @@ def test_eval(
     ]

     bbc = BugBearChecker(filename=str(path), options=options)
-    errors = [e for e in bbc.run() if (test == "B950" or not e[2].startswith("B950"))]
+    # Suppress SyntaxWarnings for B012 tests which intentionally contain
+    # return/break/continue in finally blocks (SyntaxWarning in Python 3.14+)
+    with warnings.catch_warnings():
+        if test.startswith("B012"):
+            warnings.filterwarnings("ignore", category=SyntaxWarning)
+        errors = [e for e in bbc.run() if (test == "B950" or not e[2].startswith("B950"))]
     errors.sort()
     assert errors == tuple_expected

• Should we just supress B012 and eventually retire it once we're >=3.14 project? Is that the right thing to do?

[JelleZijlstra]

Should we just supress B012 and eventually retire it once we're >=3.14 project? Is that the right thing to do?

Catching this in linters is still going to be helpful; the SyntaxWarning has some practical issues that make it not work as well as it ideally should.

[cooperlees]

Ok, should we just suppress the warnings in the testing code or leave them?

[JelleZijlstra]

I'd suppress them.