test_stream_shutdown_hung_task_prevents_cancellation was added as part of this issue. Seems to be a random error : https://ci.appveyor.com/project/python/cpython/builds/24901585

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ERROR: test_stream_shutdown_hung_task_prevents_cancellation (test.test_asyncio.test_streams.StreamTests)
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Traceback (most recent call last):
  File "C:\projects\cpython\lib\asyncio\windows_events.py", line 453, in finish_recv
    return ov.getresult()
OSError: [WinError 64] The specified network name is no longer available
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "C:\projects\cpython\lib\test\test_asyncio\test_streams.py", line 1605, in test_stream_shutdown_hung_task_prevents_cancellation
    self.loop.run_until_complete(test())
  File "C:\projects\cpython\lib\asyncio\base_events.py", line 608, in run_until_complete
    return future.result()
  File "C:\projects\cpython\lib\test\test_asyncio\test_streams.py", line 1601, in test
    await task
  File "C:\projects\cpython\lib\test\test_asyncio\test_streams.py", line 1586, in client
    self.assertEqual(b'', await stream.readline())
  File "C:\projects\cpython\lib\asyncio\streams.py", line 1545, in readline
    line = await self.readuntil(sep)
  File "C:\projects\cpython\lib\asyncio\streams.py", line 1638, in readuntil
    await self._wait_for_data('readuntil')
  File "C:\projects\cpython\lib\asyncio\streams.py", line 1521, in _wait_for_data
    await self._waiter
  File "C:\projects\cpython\lib\asyncio\proactor_events.py", line 279, in _loop_reading
    data = fut.result()
  File "C:\projects\cpython\lib\asyncio\windows_events.py", line 808, in _poll
    value = callback(transferred, key, ov)
  File "C:\projects\cpython\lib\asyncio\windows_events.py", line 457, in finish_recv
    raise ConnectionResetError(*exc.args)
ConnectionResetError: [WinError 64] The specified network name is no longer available
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