Deadlock on exception in call_later callback, during sleeping

[shamrin]

The following deadlocks:

    @pytest.mark.trio
    async def test_raise_sleeping(self, loop):
        def raise_exc():
            raise Exception()

        async def raise_sleeping():
            loop.call_later(0.1, raise_exc)
            await asyncio.sleep(0.2)

        await trio_asyncio.aio_as_trio(raise_sleeping, loop=loop)()

It gets stuck in run_aio_future on wait_task_rescheduled after it hits abort_cb callback:

trio-asyncio/trio_asyncio/_util.py

Lines 34 to 45 in b93c320

	def abort_cb(raise_cancel_arg):
	# Save the cancel-raising function
	nonlocal raise_cancel
	raise_cancel = raise_cancel_arg
	# Attempt to cancel our future
	future.cancel()
	# Keep waiting
	return trio.lowlevel.Abort.FAILED
	try:
	res = await trio.lowlevel.wait_task_rescheduled(abort_cb)
	return res

The problem exist at least since release 0.11.0.

#88 is potential similar.

(Extracted from #103.)