From https://bugs.python.org/issue44206 :

  File "/home/mark/repos/cpython/Lib/inspect.py", line 1154, in walktree
    classes.sort(key=attrgetter('__module__', '__name__'))
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: '<' not supported between instances of 'str' and 'module'


I can reproduce that failure with a debug build and either of
./python -m test -R 3:3  test_inspect
./python -m test test_inspect -F

I'm bisecting

f468ede4a2b7ab5c72ae85ab04cb56904300cd23 is the first bad commit
commit f468ede4a2b7ab5c72ae85ab04cb56904300cd23
Author: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>
Date:   Fri Jul 30 10:46:42 2021 -0700

    bpo-44648: Fix error type in inspect.getsource() in interactive session (GH-27171) (GH-27495)

    (cherry picked from commit 48a62559dfaf775e4f1cc56b19379c799e8e2587)

    Co-authored-by: andrei kulakov <andrei.avk@gmail.com>

 Lib/inspect.py                                          |  2 ++
 Lib/test/test_inspect.py                                | 17 ++++++++++++++++-
 .../Library/2021-07-15-16-51-32.bpo-44648.2o49TB.rst    |  3 +++
 3 files changed, 21 insertions(+), 1 deletion(-)
 create mode 100644 bpo-44648.2o49TB.rst">Misc/NEWS.d/next/Library/2021-07-15-16-51-32.bpo-44648.2o49TB.rst

The reason buildbots have not catched this is because the re-run login seems to not detect the problem on the second run:

./python.exe -m test test_inspect -j 1 -u all -W --slowest --fail-env-changed --timeout=11700 -R 3:3 -u-cpu -w

WARNING: Disable --verbose3 because it's incompatible with --huntrleaks: see http://bugs.python.org/issue27103
0:00:00 load avg: 2.73 Run tests in parallel using 1 child processes (timeout: 3 hour 15 min, worker timeout: 3 hour 20 min)
0:00:03 load avg: 2.92 [1/1/1] test_inspect failed (1 error)
beginning 6 repetitions
123456
.test test_inspect failed -- Traceback (most recent call last):
  File "/Users/pgalindo3/github/cpython/Lib/test/test_inspect.py", line 398, in test_getclasses
    tree = inspect.getclasstree([cls[1] for cls in classes])
  File "/Users/pgalindo3/github/cpython/Lib/inspect.py", line 1185, in getclasstree
    return walktree(roots, children, None)
  File "/Users/pgalindo3/github/cpython/Lib/inspect.py", line 1158, in walktree
    results.append(walktree(children[c], children, c))
  File "/Users/pgalindo3/github/cpython/Lib/inspect.py", line 1154, in walktree
    classes.sort(key=attrgetter('__module__', '__name__'))
TypeError: '<' not supported between instances of 'str' and 'module'

== Tests result: FAILURE ==

10 slowest tests:
- test_inspect: 3.4 sec

1 test failed:
    test_inspect

1 re-run test:
    test_inspect

0:00:03 load avg: 2.92 Re-running failed tests in verbose mode
0:00:03 load avg: 2.92 Re-running test_inspect in verbose mode (matching: test_getclasses)
beginning 6 repetitions
123456
test_getclasses (test.test_inspect.TestRetrievingSourceCode) ... ok

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

Ran 1 test in 0.001s

OK
.test_getclasses (test.test_inspect.TestRetrievingSourceCode) ... ok

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

Ran 1 test in 0.001s

OK
.test_getclasses (test.test_inspect.TestRetrievingSourceCode) ... ok

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

Ran 1 test in 0.001s

OK
.test_getclasses (test.test_inspect.TestRetrievingSourceCode) ... ok

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

Ran 1 test in 0.001s

OK
.test_getclasses (test.test_inspect.TestRetrievingSourceCode) ... ok

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

Ran 1 test in 0.001s

OK
.test_getclasses (test.test_inspect.TestRetrievingSourceCode) ... ok

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

Ran 1 test in 0.001s

OK
.

== Tests result: FAILURE then SUCCESS ==

1 test OK.

10 slowest tests:
- test_inspect: 3.4 sec

Total duration: 4.6 sec
Tests result: FAILURE then SUCCESS

Check for instance the logs in https://buildbot.python.org/all/#/builders/679/builds/92/steps/5/logs/stdio

From f468ede4a2b7ab5c72ae85ab04cb56904300cd23:

This code looks quite dangerous:

class TestGetsourceInteractive(unittest.TestCase):
    def tearDown(self):
        mod.ParrotDroppings.__module__ = mod
        sys.modules['__main__'] = self.main

That is modifing sys.modules globally!

Ah, the problem is that:

        mod.ParrotDroppings.__module__ = mod

is wrong: `__module__` must be a string, not a module object

PR 27544 just addresses the main problem, but I still have concerns about the test affecting sys.modules directly, making it dangerous to run in parallel.

With PR 27544:

❯ ./python.exe -m test test_inspect -R :
0:00:00 load avg: 2.91 Run tests sequentially
0:00:00 load avg: 2.91 [1/1] test_inspect
beginning 9 repetitions
123456789
.........

== Tests result: SUCCESS ==

1 test OK.

Total duration: 13.7 sec
Tests result: SUCCESS

New changeset 626d397cc1612ea5eef153dd910834c2ee00ddbd by Pablo Galindo Salgado in branch 'main':
bpo-44808: Fix test_inspect in refleak mode (GH-27544)
https://github.com/python/cpython/commit/626d397cc1612ea5eef153dd910834c2ee00ddbd

Pablo: thanks for investigating and fixing this, I will look for examples of changing or patching sys.modules in the testsuite to see how to avoid global effects. I think we can keep this issue open for the follow-up discussion / fix?

New changeset a1eaa74d9dcd973ec278cefc22aac7f514faee4b by Miss Islington (bot) in branch '3.10':
bpo-44808: Fix test_inspect in refleak mode (GH-27544)
https://github.com/python/cpython/commit/a1eaa74d9dcd973ec278cefc22aac7f514faee4b

I've been looking into avoiding global modification of modules['__main__'], the options are:

 1. remove the test and leave it at that

 2. remove the test and open a new issue for re-adding a test ; and look for a way to do it safely

 3. create a temp script file, add code to it that creates a class, sets `sys.modules['__main__'].__file__ = None` and inspects the class, and run this module in a new interpreter, checks exception raised and does sys.exit(1); and check the exit code after running this script.

 4. patch inspect.sys.modules; as far as I understand, this would mean other modules accessing sys.modules in other threads won't be affected, and sys.modules['__main__'] is currently used in inspect in a very limited way, so it can probably be shown that this patching won't affect other tests that use inspect, -- but I would need to look more into this.

I'm not sure if #3 is too heavy/complex for this test.

The advantage of #1 and #2 is that it's easy to do and ensures that there won't be strange random test failures that are hard to track down and debug (which is something that I'm afraid can happen right now, caused by this test).

#4 I've added to get comments / thought.

Please disregard my last comment, I think I found a good way to fix it, the PR is up here:
https://github.com/python/cpython/pull/27571/files

New changeset 58325971de0faf330c9c38269dae8315a0746e59 by andrei kulakov in branch 'main':
bpo-44808: fixes test for interactive inspect getsource of a class (GH-27571)
https://github.com/python/cpython/commit/58325971de0faf330c9c38269dae8315a0746e59

New changeset bc2841c7a9fe2b05ef77ebdf77701188dc83b2ce by Miss Islington (bot) in branch '3.10':
bpo-44808: fixes test for interactive inspect getsource of a class (GH-27571)
https://github.com/python/cpython/commit/bc2841c7a9fe2b05ef77ebdf77701188dc83b2ce