asyncio: BaseSelectorEventLoop.close() now closes the self-pipe before calling
the parent close() method. If the event loop is already closed, the self-pipe
is not unregistered from the selector.
(Merge 3.4) asyncio: BaseSelectorEventLoop.close() now closes the self-pipe
before calling the parent close() method. If the event loop is already closed,
the self-pipe is not unregistered from the selector.