test_asyncio: test_unhandled_exceptions() fails on x86-64 macOS 3.x buildbot

[vstinner]

Apparently, the test is new and was added by PR #111601.

cc @kumaraditya303

Logs:

test_unhandled_exceptions (test.test_asyncio.test_streams.StreamTests.test_unhandled_exceptions) ... Warning -- threading_cleanup() failed to cleanup 1 threads (count: 1, dangling: 2)
Warning -- Dangling thread: <_MainThread(MainThread, started 4648830464)>
ok

build: https://buildbot.python.org/all/#/builders/366/builds/5796

Linked PRs

• gh-111644: Fix asyncio test_unhandled_exceptions() #111713
• gh-111644: Enhance support threading_cleanup() #111714
• [3.12] gh-111644: Fix support threading_cleanup() (GH-111714) #111716
• [3.11] gh-111644: Fix support threading_cleanup() (GH-111714) #111717
• [3.12] gh-111644: Fix asyncio test_unhandled_exceptions() (GH-111713) #111718

[vstinner]

Oh, test fails on tons of buildbots: #111601 (comment)

[kumaraditya303]

I am not able to reproduce it on my system. Also I don't understand what Warning -- Dangling thread: <_MainThread(MainThread, started 4648830464)> means, how can main thread be considered dangling?

[vstinner]

I am not able to reproduce it on my system. Also I don't understand what Warning -- Dangling thread: <_MainThread(MainThread, started 4648830464)> means,

It usually means that a test spawns a thread and don't fully wait until the thread completes.

[vstinner]

I can reproduce the issue with the command:

./python -m test test_asyncio.test_streams -m test_unhandled_exceptions -v -j10 --fail-env-changed -F