test_epoll.test_control_and_wait() failed once on aarch64 RHEL8 Refleaks 3.9:
https://buildbot.python.org/all/#/builders/247/builds/32

This buildbot runs test_epoll 6 times in a row and the system load was quite high (10.39).

0:03:01 load avg: 10.39 [ 97/425/1] test_epoll failed -- running: test_multiprocessing_fork (3 min), test_gdb (46.3 sec), test_peg_generator (1 min 25 sec), test_capi (2 min 26 sec), test_weakref (2 min 1 sec), test_statistics (1 min 6 sec), test_multiprocessing_spawn (2 min 44 sec), test_io (1 min 53 sec)
beginning 6 repetitions
123456
...test test_epoll failed -- Traceback (most recent call last):
  File "/home/buildbot/buildarea/3.9.cstratak-RHEL8-aarch64.refleak/build/Lib/test/test_epoll.py", line 199, in test_control_and_wait
    self.assertEqual(events, expected)
AssertionError: Lists differ: [(5, 5)] != [(4, 5), (5, 5)]

First differing element 0:
(5, 5)
(4, 5)

Second list contains 1 additional elements.
First extra element 1:
(5, 5)

- [(5, 5)]
+ [(4, 5), (5, 5)]