Intermittent iOS buildbot failure in test_preauth_data_to_tls_server

[mhsmith]

Bug report

Bug description:

@freakboy3742: The buildbot has failed test_preauth_data_to_tls_server in 3 out of the last 5 runs on the main branch:

AssertionError: 'before TLS handshake with data' not found in '[SSL: RECORD_LAYER_FAILURE] record layer failure (_ssl.c:1109)'

There are also a lot of other SSL warnings and errors in the logs, but I don't know if they're related.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Other

Linked PRs

• gh-148508: Add resilience to SSL preauth tests on iOS #148536
• [3.14] gh-148508: Add resilience to SSL preauth tests on iOS (GH-148536) #148539
• [3.13] gh-148508: Add resilience to SSL preauth tests on iOS (GH-148536) #148540

[freakboy3742]

Not sure what is causing this - it seems to be related to the switch to testing the full XCframework in the buildbot (since we're not seeing the same failures in GitHub Actions CI, and we didn't see this failure prior to the switch). Most of the time, the same test passes on a re-run (which is the warning on the build). I'll do some poking around to see if I can reproduce the problem.

[freakboy3742]

After investigation; the other SSL errors are expected (and are the thing being tested; the exceptions appear in the output in verbose mode.

The error being raised appears to be part of a cluster of issues where there's already some skip handling for non-Linux platforms. When I run locally, I'm reliably hitting that skip handling (which is why the error isn't reproducible). On the buildbot, conditions are evidently slightly different, and the error being manifested is slightly different.

[freakboy3742]

For posterity - the full test failure is:

====================================================================== 
FAIL: test_preauth_data_to_tls_server (test.test_ssl.TestPreHandshakeClose.test_preauth_data_to_tls_server) 
---------------------------------------------------------------------- 
Traceback (most recent call last):
   File "/Users/buildbot/Library/Developer/CoreSimulator/Devices/4F9AFDE7-A49A-46AD-B161-FCA22E48EA55/data/Containers/Bundle/Application/65366177-2141-4935-B3D8-41FD90FA40BF/iOSTestbed.app/python/lib/python3.15/test/test_ssl.py", line 5624, 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:1109)' 
---------------------------------------------------------------------- 
Ran 209 tests in 21.815s  FAILED (failures=1, skipped=16) test test_ssl failed