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How to reproduce: Run the following program:
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import asyncio
async def handle_connection(reader, writer):
 try:
 await reader.readexactly(42)
 except BaseException as err:
 print('Interesting: %r.' % err)
 raise
 finally:
 writer.close()
loop = asyncio.get_event_loop()
coro = asyncio.start_server(handle_connection, '127.0.0.1', 8888)
server = loop.run_until_complete(coro)
try:
 loop.run_forever()
except KeyboardInterrupt:
 print('KeyboardInterrupt catched.')
server.close()
loop.run_until_complete(server.wait_closed())
loop.close()
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0. Python 3.5.2
1. Connect using telnet to localhost and port 888, type one short line and press Enter.
2. Type Ctrl+C in terminal where programw is running.
3. You will see the following output:
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^CKeyboardInterrupt catched.
Interesting: GeneratorExit().
Exception ignored in: <coroutine object handle_connection at 0x7fa6a1d91b48>
Traceback (most recent call last):
 File "bug.py", line 12, in handle_connection
 writer.close()
 File "/usr/lib/python3.5/asyncio/streams.py", line 306, in close
 return self._transport.close()
 File "/usr/lib/python3.5/asyncio/selector_events.py", line 591, in close
 self._loop.call_soon(self._call_connection_lost, None)
 File "/usr/lib/python3.5/asyncio/base_events.py", line 567, in call_soon
 handle = self._call_soon(callback, args)
 File "/usr/lib/python3.5/asyncio/base_events.py", line 576, in _call_soon
 self._check_closed()
 File "/usr/lib/python3.5/asyncio/base_events.py", line 356, in _check_closed
 raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed
Task was destroyed but it is pending!
task: <Task pending coro=<handle_connection() done, defined at bug.py:4> wait_for=<Future pending cb=[Task._wakeup()]>>
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This is almost canonical example of asyncio usage. So I have two questions:
1. Why coroutine is interrupted with GeneratorExit instead of CancelledError ?
2. Why something happend AFTER io loop is closed ?
3. How to code all that right ? I want to close connection on any error. Example provided is simplified code. In real code it looks like:
=====
 try:
 await asyncio.wait_for(self._handle_connection(reader, writer), 60)
 except asyncio.TimeoutError:
 writer.transport.abort()
 except asyncio.CancelledError:
 writer.transport.abort()
 except Exception:
 writer.transport.abort()
 finally:
 writer.close()
=====

I've also been affected by this and found that if you use asyncio.run() the coroutine is interrupted with a CancelledError as you'd expect. The following script shows that
=======================
import asyncio
async def handle_connection(reader, writer):
 try:
 await reader.readexactly(42)
 except BaseException as err:
 print('Interesting: %r.' % err)
 raise
 finally:
 writer.close()
async def main():
 listener = await asyncio.start_server(handle_connection, '127.0.0.1', 8888)
 try:
 async with listener:
 await listener.serve_forever()
 except KeyboardInterrupt:
 print('KeyboardInterrupt')
asyncio.run(main())
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