Check that cothread isn't passed an async function

Author: AlexanderWells-diamond

softioc/cothread_dispatcher.py

@@ -38,4 +38,7 @@ def wrapper():
                 if completion:
                     completion(*completion_args)
 
+        assert not inspect.iscoroutinefunction(func)
+        assert not inspect.iscoroutinefunction(completion)
+
         self.__dispatcher(wrapper)