The BaseSelectorEventLoop class (inherited by UnixSelectorEventLoop) creates a socketpair in its constructor. So if you don't call close(), the socketpair may stay alive.

It would be convinient to support the context manager to be able to write:

with asyncio.get_event_loop() as loop
   # ... prepare loop ...
   loop.run_forever()
# KeyboardInterrupt or SystemExit: loop.close() is called

Hello World examples don't call close(), so the sockets are not closed when the example is stopped using CTRL+c.

Attached patch adds __enter__/__exit__ methods to BaseEventLoop and use it in the two Hello World examples.