test_multiprocessing.test_empty_authkey triggers env changed failure

[colesbury]

The test starts a thread but doesn't join it, which can lead to test failures with "ENV CHANGED"

cpython/Lib/test/_test_multiprocessing.py

Lines 3518 to 3521 in c62144a

	with self.connection.Listener(authkey=key) as listener:
	threading.Thread(target=run, args=(listener.address, key)).start()
	with listener.accept() as d:
	self.assertEqual(d.recv(), 1729)

See also #25845

From https://buildbot.python.org/all/#/builders/249/builds/7957/steps/5/logs/stdio:

...
test_empty_authkey (test.test_multiprocessing_fork.test_processes.WithProcessesTestListener.test_empty_authkey) ... ok
test_multiple_bind (test.test_multiprocessing_fork.test_processes.WithProcessesTestListener.test_multiple_bind) ... ok
Warning -- Dangling threads:{<Thread(Thread-13 (run), started 139968890533568)>}
...

Linked PRs

• gh-116439: Ensure thread is joined in test_empty_authkey #116442

[colesbury]

Already fixed in #116434