Race with KeyboardInterrupt in asyncio loop run_forever() method

[hetmankp]

There is a race with the KeyboardInterrupt exception in the asyncio.base_events.BaseEventLoop.run_forever() method. While an attempt is made to restore the environment to its previous state before run_forever() completes with a try...finally, a couple items find themselves outside the try...finally. Specifically, a badly timed KeyboardInterrupt will mean that, neither the self._thread_id value or the hooks set by sys.set_asyncgen_hooks() will be correctly restored. Both of these should be moved inside the try...finally.

cpython/Lib/asyncio/base_events.py

Lines 596 to 600 in c9118af

	self._thread_id = threading.get_ident()
	old_agen_hooks = sys.get_asyncgen_hooks()
	sys.set_asyncgen_hooks(firstiter=self._asyncgen_firstiter_hook,
	finalizer=self._asyncgen_finalizer_hook)

This applies to all existing version of Python on all platforms.