stop test_cancel_sleep from deadlocking and less dependent on timer

No need for `raise Exception` because we already assert the flag.

fixes #103

Author: shamrin

tests/test_misc.py

@@ -154,11 +154,10 @@ async def test_cancel_sleep(self, loop):
         def do_not_run():
             nonlocal owch
             owch = 1
-            raise Exception("should not run")
 
         async def cancel_sleep():
             h = loop.call_later(0.2, do_not_run)
-            await asyncio.sleep(0.1)
+            await asyncio.sleep(0.01)
             h.cancel()
             await asyncio.sleep(0.3)