The commit 369a1cbdee14d9f27356fb3a8bb21e4fde289d25 introduces a change in environment. I haven't checked the other PR though to see if this is fixed.

./python.exe -m test --fail-env-changed test_codeop -m test_warning
0:00:00 load avg: 2.30 Run tests sequentially
0:00:00 load avg: 2.30 [1/1] test_codeop
Warning -- warnings.filters was modified by test_codeop
  Before: (4331716096, [('default', None, <class 'DeprecationWarning'>, '__main__', 0), ('ignore', None, <class 'DeprecationWarning'>, None, 0), ('ignore', None, <class 'PendingDeprecationWarning'>, None, 0), ('ignore', None, <class 'ImportWarning'>, None, 0), ('ignore', None, <class 'ResourceWarning'>, None, 0)], [('default', None, <class 'DeprecationWarning'>, '__main__', 0), ('ignore', None, <class 'DeprecationWarning'>, None, 0), ('ignore', None, <class 'PendingDeprecationWarning'>, None, 0), ('ignore', None, <class 'ImportWarning'>, None, 0), ('ignore', None, <class 'ResourceWarning'>, None, 0)])
  After:  (4331716096, [('default', None, <class 'DeprecationWarning'>, '__main__', 0), ('ignore', None, <class 'DeprecationWarning'>, None, 0), ('ignore', None, <class 'PendingDeprecationWarning'>, None, 0), ('ignore', None, <class 'ImportWarning'>, None, 0), ('ignore', None, <class 'ResourceWarning'>, None, 0)], [('error', None, <class 'SyntaxWarning'>, None, 0), ('default', None, <class 'DeprecationWarning'>, '__main__', 0), ('ignore', None, <class 'DeprecationWarning'>, None, 0), ('ignore', None, <class 'PendingDeprecationWarning'>, None, 0), ('ignore', None, <class 'ImportWarning'>, None, 0), ('ignore', None, <class 'ResourceWarning'>, None, 0)])
test_codeop failed (env changed)

== Tests result: ENV CHANGED ==

1 test altered the execution environment:
    test_codeop

Total duration: 38 ms
Tests result: ENV CHANGED


On an unrelated note the test passes with verbose mode though fail-env-changed flag is passed.

./python.exe -m test --fail-env-changed test_codeop -m test_warning -vvv
== CPython 3.10.0a0 (heads/master:c51db0ea40d, Aug 13 2020, 15:47:27) [Clang 10.0.1 (clang-1001.0.46.4)]
== macOS-10.14.6-x86_64-i386-64bit little-endian
== cwd: /Users/kasingar/stuff/python/cpython/build/test_python_29945æ
== CPU count: 8
== encodings: locale=UTF-8, FS=utf-8
0:00:00 load avg: 1.53 Run tests sequentially
0:00:00 load avg: 1.53 [1/1] test_codeop
test_warning (test.test_codeop.CodeopTests) ... ok

----------------------------------------------------------------------

Ran 1 test in 0.001s

OK

== Tests result: SUCCESS ==

1 test OK.

Total duration: 58 ms
Tests result: SUCCESS