gh-104090: Add exit code to multiprocessing ResourceTracker (GH-115410)

This builds on https://github.com/python/cpython/pull/106807, which adds
a return code to ResourceTracker, to make future debugging easier.
Testing this “in situ” proved difficult, since the global ResourceTracker is
involved in test infrastructure. So, the tests here create a new instance and
feed it fake data.

---------

Co-authored-by: Yonatan Bitton <yonatan.bitton@perception-point.io>
Co-authored-by: Yonatan Bitton <bityob@gmail.com>
Co-authored-by: Antoine Pitrou <antoine@python.org>

Lib/test/test_concurrent_futures/test_init.py

@@ -3,6 +3,7 @@ import logging
 import queue
 import time
 import unittest
+import sys
 from concurrent.futures._base import BrokenExecutor
 from logging.handlers import QueueHandler
 
@@ -109,6 +110,31 @@ create_executor_tests(globals(), InitializerMixin)
 create_executor_tests(globals(), FailingInitializerMixin)
 
 
+@unittest.skipIf(sys.platform == "win32", "Resource Tracker doesn't run on Windows")
+class FailingInitializerResourcesTest(unittest.TestCase):
+    """
+    Source: https://github.com/python/cpython/issues/104090
+    """
+
+    def _test(self, test_class):
+        runner = unittest.TextTestRunner()
+        runner.run(test_class('test_initializer'))
+
+        # GH-104090:
+        # Stop resource tracker manually now, so we can verify there are not leaked resources by checking
+        # the process exit code
+        from multiprocessing.resource_tracker import _resource_tracker
+        _resource_tracker._stop()
+
+        self.assertEqual(_resource_tracker._exitcode, 0)
+
+    def test_spawn(self):
+        self._test(ProcessPoolSpawnFailingInitializerTest)
+
+    def test_forkserver(self):
+        self._test(ProcessPoolForkserverFailingInitializerTest)
+
+
 def setUpModule():
     setup_module()