trio

- race conditions with channels
- aenumerate

What the hell:

	async with trio.open_nursery() as nursery:
	    nursery.cancel_scope.cancel()
	    print('going to sleep')
	    await trio.sleep(2)
	    print('this never runs, and does not sleep')

---

To cancel a nursery, but check what's running just before:
	
	def cancel_after(nursery, timeout):
		await trio.sleep(timeout)
		print(nursery.child_tasks)
		nursery.cancel_scope.cancel()

	with trio.open_nursery() as nursery:
		nursery.start_soon(task1)
		nursery.start_soon(task2)
		nursery.start_soon(cancel_after, nursery, 2)

TO FIX: it keeps the nursery open even if all the other tasks exits