bpo-41710: Document _PyTime_t API in pytime.h

[vstinner]

https://bugs.python.org/issue41710

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot PPC64LE Fedora Stable 3.x has failed when building commit b34dd58.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/90/builds/672) and take a look at the build logs.
4. Check if the failure is related to this commit (b34dd58) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/90/builds/672

Failed tests:

• test_unicodedata

Failed subtests:

• test_normalization - test.test_unicodedata.NormalizationTest

Summary of the results of the build (if available):

== Tests result: FAILURE then FAILURE ==

414 tests OK.

10 slowest tests:

• test_urllib2net: 14 min 55 sec
• test_hashlib: 14 min 34 sec
• test_codecmaps_jp: 7 min 43 sec
• test_codecmaps_kr: 6 min 26 sec
• test_codecmaps_cn: 6 min 25 sec
• test_codecmaps_tw: 3 min 59 sec
• test_gdb: 3 min 38 sec
• test_peg_generator: 3 min 20 sec
• test_multiprocessing_spawn: 3 min 7 sec
• test_concurrent_futures: 3 min 1 sec

1 test failed:
test_unicodedata

12 tests skipped:
test_devpoll test_ioctl test_kqueue test_msilib test_startfile
test_tix test_tk test_ttk_guionly test_winconsoleio test_winreg
test_winsound test_zipfile64

1 re-run test:
test_unicodedata

Total duration: 19 min 10 sec

Click to see traceback logs

Traceback (most recent call last):
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-ppc64le/build/Lib/test/test_unicodedata.py", line 336, in test_normalization
    testdata = open_urlresource(TESTDATAURL, encoding="utf-8",
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TimeoutError: timed out


Traceback (most recent call last):
  File "/home/buildbot/buildarea/3.x.cstratak-fedora-stable-ppc64le/build/Lib/test/test_unicodedata.py", line 342, in test_normalization
    self.fail(f"Could not retrieve {TESTDATAURL}")
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: Could not retrieve http://www.pythontest.net/unicode/14.0.0/NormalizationTest.txt