`test_threading.test_interrupt_main_subthread`: release unlocked lock

Bug report

======================================================================
ERROR: test_interrupt_main_subthread (test.test_threading.InterruptMainTests.test_interrupt_main_subthread)
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Traceback (most recent call last):
  File "/Users/ec2-user/buildbot/buildarea/3.x.itamaro-macos-arm64-aws.macos-with-brew.refleak.nogil/build/Lib/threading.py", line 659, in wait
    signaled = self._cond.wait(timeout)
               ~~~~~~~~~~~~~~~^^^^^^^^^
  File "/Users/ec2-user/buildbot/buildarea/3.x.itamaro-macos-arm64-aws.macos-with-brew.refleak.nogil/build/Lib/threading.py", line 368, in wait
    self._acquire_restore(saved_state)
    ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/Users/ec2-user/buildbot/buildarea/3.x.itamaro-macos-arm64-aws.macos-with-brew.refleak.nogil/build/Lib/threading.py", line 315, in _acquire_restore
    def _acquire_restore(self, x):
    
KeyboardInterrupt
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "/Users/ec2-user/buildbot/buildarea/3.x.itamaro-macos-arm64-aws.macos-with-brew.refleak.nogil/build/Lib/test/test_threading.py", line 2035, in test_interrupt_main_subthread
    t.start()
    ~~~~~~~^^
  File "/Users/ec2-user/buildbot/buildarea/3.x.itamaro-macos-arm64-aws.macos-with-brew.refleak.nogil/build/Lib/threading.py", line 977, in start
    self._started.wait()  # Will set ident and native_id
    ~~~~~~~~~~~~~~~~~~^^
  File "/Users/ec2-user/buildbot/buildarea/3.x.itamaro-macos-arm64-aws.macos-with-brew.refleak.nogil/build/Lib/threading.py", line 656, in wait
    with self._cond:
    ...<3 lines>...
        return signaled
  File "/Users/ec2-user/buildbot/buildarea/3.x.itamaro-macos-arm64-aws.macos-with-brew.refleak.nogil/build/Lib/threading.py", line 307, in __exit__
    return self._lock.__exit__(*args)
           ~~~~~~~~~~~~~~~~~~~^^^^^^^
RuntimeError: release unlocked lock
----------------------------------------------------------------------

Seen on the ARM64 macOS nogil refleaks buildbot:

https://buildbot.python.org/all/#/builders/1368/builds/865/steps/5/logs/stdio

Reported by encoku

Linked PRs

• gh-118485

Start with Lib/test/test_threading.py at InterruptMainTests.test_interrupt_main_subthread and the wait and start paths in Lib/threading.py shown in the traceback. Reproduce the ARM64 macOS nogil buildbot failure if possible, then inspect linked PR gh-118485 and the related discussion. Done means the test no longer reports the unlocked-lock error without regressing threading behavior.