gh-129354: Use PyErr_FormatUnraisable() function

[vstinner]

Replace PyErr_WriteUnraisable() with PyErr_FormatUnraisable().

• Issue: Replace PyErr_WriteUnraisable() with PyErr_FormatUnraisable() #129354

[serhiy-storchaka]

Does repr always work at that stage of finalization?

[vstinner]

Does repr always work at that stage of finalization?

I hope so. Before this change, repr() was already used. It's not something new. Only the error message is changed.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot ARM64 macOS 3.x has failed when building commit 14489c1.

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/#/builders/725/builds/9664) and take a look at the build logs.
4. Check if the failure is related to this commit (14489c1) 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/#/builders/725/builds/9664

Failed tests:

• test.test_multiprocessing_spawn.test_processes

Failed subtests:

• test_repr_rlock - test.test_multiprocessing_spawn.test_processes.WithProcessesTestLock.test_repr_rlock
• test_preauth_data_to_tls_server - test.test_ssl.TestPreHandshakeClose.test_preauth_data_to_tls_server

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

==

Click to see traceback logs

Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/_test_multiprocessing.py", line 1530, in test_repr_rlock
    self.assertEqual('<RLock(SomeOtherThread, nonzero)>', repr(lock))
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: '<RLock(SomeOtherThread, nonzero)>' != '<RLock(None, 0)>'
- <RLock(SomeOtherThread, nonzero)>
+ <RLock(None, 0)>


Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/test_ssl.py", line 5094, in test_preauth_data_to_tls_server
    self.assertIn("before TLS handshake with data", wrap_error.args[1])
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 'before TLS handshake with data' not found in '[SSL: RECORD_LAYER_FAILURE] record layer failure (_ssl.c:1066)'