gh-92886: Fix tests that fail when running with optimizations (-O) in _test_multiprocessing.py

[jackh-ncl]

#92886

Before:

$ ./python.exe -Om unittest test._test_multiprocessing ...........s.............s........F..F................ ====================================================================== FAIL: test_dict (test._test_multiprocessing.TestSyncManagerTypes.test_dict) ---------------------------------------------------------------------- Traceback (most recent call last): File "/Users/.../dev/cpython/Lib/test/_test_multiprocessing.py", line 5726, in test_dict self.assertEqual(len(o), 0) ^^^^^^^^^^^^^^^^^^^^^^^^^^^ AssertionError: 1 != 0 ====================================================================== FAIL: test_list (test._test_multiprocessing.TestSyncManagerTypes.test_list) ---------------------------------------------------------------------- Traceback (most recent call last): File "/Users/.../dev/cpython/Lib/test/_test_multiprocessing.py", line 5708, in test_list self.assertEqual(len(o), 0) ^^^^^^^^^^^^^^^^^^^^^^^^^^^ AssertionError: 1 != 0 ---------------------------------------------------------------------- Ran 54 tests in 24.460s FAILED (failures=2, skipped=2)

After:

$ ./python.exe -Om unittest test._test_multiprocessing ...........s.............s............................ ---------------------------------------------------------------------- Ran 54 tests in 24.588s OK (skipped=2)

[bedevere-bot]

Most changes to Python require a NEWS entry.

Please add it using the blurb_it web app or the blurb command-line tool.

[jackh-ncl]

Could be worth changing the rest of the assertions in this file?

[iritkatriel]

Thanks.