test_urllib failed and then passed when re-run on s390x RHEL7 Refleaks 3.x:
https://buildbot.python.org/all/#builders/129/builds/300

I can reproduce the issue on my Linux laptop:

$ ./python -m test -m unittest.test.test_break.TestBreakDefaultIntHandler.testInterruptCaught test_unittest -F
0:00:00 load avg: 1.52 Run tests sequentially
0:00:00 load avg: 1.52 [  1] test_unittest
0:00:00 load avg: 1.52 [  2] test_unittest
0:00:00 load avg: 1.52 [  3] test_unittest
0:00:00 load avg: 1.52 [  4] test_unittest
0:00:00 load avg: 1.52 [  5] test_unittest
0:00:01 load avg: 1.52 [  6] test_unittest
0:00:01 load avg: 1.52 [  7] test_unittest
0:00:01 load avg: 1.52 [  8] test_unittest
test test_unittest failed -- Traceback (most recent call last):
  File "/home/vstinner/python/main/Lib/unittest/test/test_break.py", line 66, in testInterruptCaught
    test(result)
    ^^^^^^^^^^^^
  File "/home/vstinner/python/main/Lib/unittest/test/test_break.py", line 63, in test
    self.assertTrue(result.shouldStop)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: False is not true

test_unittest failed (1 failure)

== Tests result: FAILURE ==

7 tests OK.

1 test failed:
    test_unittest

Total duration: 1.7 sec
Tests result: FAILURE

I am trying to debug this.

Several intersting notes:
1. `time.sleep()` does not help
2. It always fails on `8`th turn
3. Changing `self.assertTrue(result.shouldStop)` to

```
msg = f'{type(result)} {vars(result)}'
self.assertTrue(result.shouldStop, msg)
```

fixes the problem.

I think this might be a side effect of https://docs.python.org/3/library/signal.html#execution-of-python-signal-handlers

> A Python signal handler does not get executed inside the low-level (C) signal handler. Instead, the low-level signal handler sets a flag which tells the virtual machine to execute the corresponding Python signal handler at a later point(for example at the next bytecode instruction). This has consequences

Other tests are also affected:
- `./python.exe -m test -m unittest.test.test_break.TestBreakDefaultIntHandler.testSecondInterrupt test_unittest -F`
- `./python.exe -m test -m unittest.test.test_break.TestBreakDefaultIntHandler.testTwoResults test_unittest -F`
- `./python.exe -m test -m unittest.test.test_break.TestBreakDefaultIntHandler.testHandlerReplacedButCalled test_unittest -F`
- etc

I think that we need a universal solution, I am going to write a helper method and add it to all tests there.

Same issue as https://bugs.python.org/issue46465, PR https://github.com/python/cpython/pull/30826 fixes this.

Oops, I forgot about my own bpo-46465. I failed to find it when I searched for "test_urllib".

New changeset e2c28616ce6c3cdb1013c415125220a0b86b86a1 by Nikita Sobolev in branch 'main':
bpo-46709: check eval breaker in specialized `CALL` opcodes (GH-31404)
https://github.com/python/cpython/commit/e2c28616ce6c3cdb1013c415125220a0b86b86a1