test_repl: Warning -- reap_children() reaped child process 3457256

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On the "AMD64 Debian PGO 3.x" buildbot worker, test_pyrepl fails with "env changed" because a child process is not awaited explicitly.

build: https://buildbot.python.org/all/#/builders/249/builds/8909

1:17:07 load avg: 20.12 [453/478/1] test_pyrepl failed (env changed) (37.4 sec)
test_empty (test.test_pyrepl.test_input.KeymapTranslatorTests.test_empty) ... ok
test_push_character_key (test.test_pyrepl.test_input.KeymapTranslatorTests.test_push_character_key) ... ok
test_push_character_key_with_stack (test.test_pyrepl.test_input.KeymapTranslatorTests.test_push_character_key_with_stack) ... ok
(...)
test.test_pyrepl.test_windows_console (unittest.loader.ModuleSkipped.test.test_pyrepl.test_windows_console) ... skipped 'test only relevant on win32'

----------------------------------------------------------------------
Ran 116 tests in 35.634s

OK (skipped=2)
Warning -- reap_children() reaped child process 3457256

Linked PRs

• gh-120635: Avoid leaking processes in test_pyrepl #120676
• [3.13] gh-120635: Avoid leaking processes in test_pyrepl (GH-120676) #120741

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Sadly, I fail to reproduce the issues locally.

[encukou]

The commits added for the first failed run were 1b62bce, 86a8a1c & 939c201. One of them adds a pyrepl test that runs a subprocess:

• gh-118908: Limit exposed globals from internal imports and definitions on new REPL startup #119547

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I managed to reproduce the issue with this change:

diff --git a/Lib/test/test_pyrepl/test_pyrepl.py b/Lib/test/test_pyrepl/test_pyrepl.py
index 41ba5959a1..0c22260741 100644
--- a/Lib/test/test_pyrepl/test_pyrepl.py
+++ b/Lib/test/test_pyrepl/test_pyrepl.py
@@ -887,7 +887,7 @@ def run_repl(self, repl_input: str | list[str], env: dict | None = None) -> tupl
         os.close(master_fd)
         os.close(slave_fd)
         try:
-            exit_code = process.wait(timeout=SHORT_TIMEOUT)
+            exit_code = process.wait(timeout=1.0)
         except subprocess.TimeoutExpired:
             process.kill()
             exit_code = process.returncode

And the command:

./python -m test test_pyrepl -u all -W -F -j100 --fail-env-changed -m test_dumb_terminal_exits_cleanly -m test_exposed_globals_in_repl

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I wrote a fix: #120676.