Good. Using PR 5291, test_asyncio doesn't hang anymore, and only 2 tests still fail:

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ERROR: test_foobar (test.test_asyncio.test_tasks.CTask_Future_Tests)
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Traceback (most recent call last):
  File "/home/vstinner/prog/python/master/Lib/test/test_asyncio/test_tasks.py", line 2473, in test_foobar
    self.loop.call_later(0.1, fut.set_result(1))
  File "/home/vstinner/prog/python/master/Lib/asyncio/base_events.py", line 509, in call_later
    context=context)
  File "/home/vstinner/prog/python/master/Lib/asyncio/base_events.py", line 522, in call_at
    self._check_callback(callback, 'call_at')
  File "/home/vstinner/prog/python/master/Lib/asyncio/base_events.py", line 556, in _check_callback
    f'a callable object was expected by {method}(), '
TypeError: a callable object was expected by call_at(), got None

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FAIL: test_nonstream_socket (test.test_asyncio.test_base_events.BaseLoopSendfileTests)
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ValueError: the socket must be non-blocking

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/vstinner/prog/python/master/Lib/test/test_asyncio/test_base_events.py", line 1922, in test_nonstream_socket
    self.run_loop(self.loop.sock_sendfile(sock, self.file))
AssertionError: "only SOCK_STREAM type" does not match "the socket must be non-blocking"

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Ran 1874 tests in 49.198s

FAILED (failures=1, errors=1, skipped=5)