Tests broken due to mktime handling (Linux + glibc)

[vcunat]

Since a glibc commit, three twisted tests started to fail: test_formatTimeDefault, test_eventAsTextTimestampOnly, test_formatTimeWithDefaultFormat.

After some talk with glibc upstream, I'm inclined to think that the root of the problem is that these tests use mktime with timezone UTC+00 and indicating daylight saving which doesn't make sense (no DST in that timezone by definition).

The tests are in https://github.com/twisted/twisted/blob/twisted-22.10.0/src/twisted/logger/test/test_format.py

Testing environment

• Linux + glibc, triggered after https://sourceware.org/git/?p=glibc.git;a=commit;h=83859e1115269cf56d21669361d4ddbe2687831c
  (also picked to some stable glibc branches). I'm using NixOS in particular, but that shouldn't be relevant really.

• twisted-22.10.0 + python-3.10.8

Failed logs:

===============================================================================
[FAIL]
Traceback (most recent call last):
  File "/nix/store/l2dwsswg8dd2ybqpxjy3a1iqsf5lj9d5-python3.10-twisted-22.10.0/lib/python3.10/site-packages/tw
isted/logger/test/test_format.py", line 251, in test_formatTimeDefault
    self.assertEqual(
  File "/nix/store/l2dwsswg8dd2ybqpxjy3a1iqsf5lj9d5-python3.10-twisted-22.10.0/lib/python3.10/site-packages/tw
isted/trial/_synctest.py", line 441, in assertEqual
    super().assertEqual(first, second, msg)
  File "/nix/store/xwz1n452s7913wj1338514lqzajmbgla-python3-3.10.8/lib/python3.10/unittest/case.py", line 845,
 in assertEqual
    assertion_func(first, second, msg=msg)
  File "/nix/store/xwz1n452s7913wj1338514lqzajmbgla-python3-3.10.8/lib/python3.10/unittest/case.py", line 1226
, in assertMultiLineEqual
    self.fail(self._formatMessage(msg, standardMsg))
twisted.trial.unittest.FailTest: '2013-09-24T10:40:47+0000 [-#-] XYZZY\n' != '2013-09-24T11:40:47+0000 [-#-] XYZZY\n'
- 2013-09-24T10:40:47+0000 [-#-] XYZZY
?             ^
+ 2013-09-24T11:40:47+0000 [-#-] XYZZY
?             ^


twisted.logger.test.test_format.ClassicLogFormattingTests.test_formatTimeDefault
===============================================================================
[FAIL]
Traceback (most recent call last):
  File "/nix/store/l2dwsswg8dd2ybqpxjy3a1iqsf5lj9d5-python3.10-twisted-22.10.0/lib/python3.10/site-packages/twisted/logger/test/test_format.py", line 589, in test_eventAsTextTimestampOnly
    self.assertEqual(
  File "/nix/store/l2dwsswg8dd2ybqpxjy3a1iqsf5lj9d5-python3.10-twisted-22.10.0/lib/python3.10/site-packages/twisted/trial/_synctest.py", line 441, in assertEqual
    super().assertEqual(first, second, msg)
  File "/nix/store/xwz1n452s7913wj1338514lqzajmbgla-python3-3.10.8/lib/python3.10/unittest/case.py", line 845, in assertEqual
    assertion_func(first, second, msg=msg)
  File "/nix/store/xwz1n452s7913wj1338514lqzajmbgla-python3-3.10.8/lib/python3.10/unittest/case.py", line 1226, in assertMultiLineEqual
    self.fail(self._formatMessage(msg, standardMsg))
twisted.trial.unittest.FailTest: '2013-09-24T10:40:47+0000 ABCD' != '2013-09-24T11:40:47+0000 ABCD'
- 2013-09-24T10:40:47+0000 ABCD
?             ^
+ 2013-09-24T11:40:47+0000 ABCD
?             ^


twisted.logger.test.test_format.EventAsTextTests.test_eventAsTextTimestampOnly
===============================================================================
[FAIL]
Traceback (most recent call last):
  File "/nix/store/l2dwsswg8dd2ybqpxjy3a1iqsf5lj9d5-python3.10-twisted-22.10.0/lib/python3.10/site-packages/twisted/logger/test/test_format.py", line 176, in test_formatTimeWithDefaultFormat
    testForTimeZone(
  File "/nix/store/l2dwsswg8dd2ybqpxjy3a1iqsf5lj9d5-python3.10-twisted-22.10.0/lib/python3.10/site-packages/twisted/logger/test/test_format.py", line 172, in testForTimeZone
    self.assertEqual(formatTime(localDST), expectedDST)
  File "/nix/store/l2dwsswg8dd2ybqpxjy3a1iqsf5lj9d5-python3.10-twisted-22.10.0/lib/python3.10/site-packages/twisted/trial/_synctest.py", line 441, in assertEqual
    super().assertEqual(first, second, msg)
  File "/nix/store/xwz1n452s7913wj1338514lqzajmbgla-python3-3.10.8/lib/python3.10/unittest/case.py", line 845, in assertEqual
    assertion_func(first, second, msg=msg)
  File "/nix/store/xwz1n452s7913wj1338514lqzajmbgla-python3-3.10.8/lib/python3.10/unittest/case.py", line 1226, in assertMultiLineEqual
    self.fail(self._formatMessage(msg, standardMsg))
twisted.trial.unittest.FailTest: '2006-06-29T23:00:00+0000' != '2006-06-30T00:00:00+0000'
- 2006-06-29T23:00:00+0000
?         ^^ ^^
+ 2006-06-30T00:00:00+0000
?         ^^ ^^


twisted.logger.test.test_format.TimeFormattingTests.test_formatTimeWithDefaultFormat
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