Summary

This PR suppresses noise and dirt from signal propagation introduced in #1600.

• Suppress tracebacks from worker/reload subprocesses on termination. These are triggered deep inside multiprocessing.process on any exception. Since the shutdown exception is expected, subprocesses spawned for workers/reload simply discard it.
  • Fixes Unexcepted behavior while reloading #2294.
• Always run cleanup of unix domain sockets when the uvicorn.run exits. This would previously be skipped on forced shutdown.

Note: I was not able to reproduce #2281 / #2289 so I do not know if they are fixed by this. However, this fixes the various reports on those discussions/issues about tracebacks.

I do not have access to a Windows machine for testing so had to emulate it. It would be nice if someone can confirm that this works on Windows. A minimal repro is the program

# test.py
async def dummy_app(scope, receive, send): pass

run via

python -m uvicorn test:dummy_app --reload

@johanboekhoven kindly tested this on Windows.

Checklist

• I understand that this PR may be closed in case there was no previous discussion. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
  • This change has no effect on behaviour, merely output.
• I've updated the documentation accordingly.
  • This change has no effect on documented behaviour.