The exception should probably be just ignored.  Andrew, thoughts?

Here's an example error traceback:

      Traceback (most recent call last):
        File "c:\projects\asyncpg\asyncpg\connection.py", line 1227, in _cancel
          await w.wait_closed()
        File "C:\Python38\lib\asyncio\streams.py", line 376, in wait_closed
          await self._protocol._get_close_waiter(self)
        File "c:\projects\asyncpg\asyncpg\connection.py", line 1202, in _cancel
          await r.read()  # Wait until EOF
        File "C:\Python38\lib\asyncio\streams.py", line 694, in read
          block = await self.read(self._limit)
        File "C:\Python38\lib\asyncio\streams.py", line 701, in read
          await self._wait_for_data('read')
        File "C:\Python38\lib\asyncio\streams.py", line 534, in _wait_for_data
          await self._waiter
        File "C:\Python38\lib\asyncio\proactor_events.py", line 280, in _loop_reading
          data = fut.result()
        File "C:\Python38\lib\asyncio\windows_events.py", line 808, in _poll
          value = callback(transferred, key, ov)
        File "C:\Python38\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