System transitions tests are skipped in datetime tester

[abalkin]

Bug report

Tests that should be conditionally skipped only when time.tzset is not present are skipped all the time.

% ./python.exe Lib/test/test_datetime.py -k test_system_transitions  -v
test_system_transitions (test.datetimetester.IranTest_Pure.test_system_transitions) ... skipped 'time module has no attribute tzset'
test_system_transitions (test.datetimetester.ZoneInfoTest_Pure.test_system_transitions) ... skipped 'time module has no attribute tzset'
test_system_transitions (test.datetimetester.ZoneInfoTest[Africa/Abidjan]_Pure.test_system_transitions) ... skipped 'time module has no attribute tzset'
test_system_transitions (test.datetimetester.ZoneInfoTest[Africa/Accra]_Pure.test_system_transitions) ... skipped 'time module has no attribute tzset'
test_system_transitions (test.datetimetester.ZoneInfoTest[Africa/Addis_Ababa]_Pure.test_system_transitions) ... skipped 'time module has no attribute tzset'
test_system_transitions (test.datetimetester.ZoneInfoTest[Africa/Algiers]_Pure.test_system_transitions) ... skipped 'time module has no attribute tzset'
...

----------------------------------------------------------------------
Ran 842 tests in 0.036s

OK (skipped=842)

Your environment

• CPython versions tested on:

  % ./python.exe
  Python 3.12.0a4+ (heads/main:04e06e20ee, Feb  3 2023, 17:55:49) [Clang 14.0.0 (clang-1400.0.29.202)] on darwin
  Type "help", "copyright", "credits" or "license" for more information.

• Operating system and architecture: macOS

Linked PRs

• Fix detection of presence of time.tzset (gh-101539) #101540

[abalkin]

It looks like the problem was introduced in #31898. I'll submit a fix shortly.