`tests_python/test_utilities.py::test_find_main_thread_id` fails

This test has started failing on Debian with both Python 3.11 and Python 3.12 (pydevd version 2.9.6 and 3.1.0) on the assertion `assert 'threading' not in sys.modules` on line 27 of `tests_python/resources/_pydevd_test_find_main_thread_id.py`.  I don't know why it should be imported; it is imported by `subprocess`, but this should be running in a fresh thread.