[3.15] gh-133651: Increase multiprocessing test_interrupt() timeout (GH-160281) (#160319)

gh-133651: Increase multiprocessing test_interrupt() timeout (GH-160281)

Increase timeout from 10 to at least 30 seconds (SHORT_TIMEOUT).
(cherry picked from commit 7ee9ddd)

Co-authored-by: Victor Stinner <vstinner@python.org>

Author: miss-islington

Lib/test/_test_multiprocessing.py

@@ -624,10 +624,10 @@ def _kill_process(self, meth, target=None):
             # On the Gentoo buildbot waitpid() often seems to block forever.
             # We use alarm() to interrupt it if it blocks for too long.
             def handler(*args):
-                raise RuntimeError('join took too long: %s' % p)
+                raise RuntimeError(f'join took longer than {timeout} seconds: {p}')
             old_handler = signal.signal(signal.SIGALRM, handler)
             try:
-                signal.alarm(10)
+                signal.alarm(int(timeout))
                 self.assertEqual(join(), None)
             finally:
                 signal.alarm(0)