Seems this failure might be back.  At least, the traceback looks quite similar to me.

The buildbot failed with this:

heads/master:85b6b70589, Mar 29 2021, 22:53:15

0:05:26 load avg: 3.95 [426/427] test_tokenize passed (56.0 sec) -- running: test_asyncio (44.8 sec)
0:05:35 load avg: 3.34 [427/427/1] test_asyncio failed (env changed) (54.1 sec)
Warning -- Unraisable exception
Exception ignored in: <function _SSLProtocolTransport.__del__ at 0x3ffa8ecedb0>
Traceback (most recent call last):
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel8-z/build/Lib/asyncio/sslproto.py", line 321, in __del__
    self.close()
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel8-z/build/Lib/asyncio/sslproto.py", line 316, in close
    self._ssl_protocol._start_shutdown()
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel8-z/build/Lib/asyncio/sslproto.py", line 590, in _start_shutdown
    self._abort()
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel8-z/build/Lib/asyncio/sslproto.py", line 731, in _abort
    self._transport.abort()
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel8-z/build/Lib/asyncio/selector_events.py", line 680, in abort
    self._force_close(None)
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel8-z/build/Lib/asyncio/selector_events.py", line 731, in _force_close
    self._loop.call_soon(self._call_connection_lost, exc)
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel8-z/build/Lib/asyncio/base_events.py", line 745, in call_soon
    self._check_closed()
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel8-z/build/Lib/asyncio/base_events.py", line 510, in _check_closed
    raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed