Get rid of the None default for memoize_default. It shouldn't have a default if not given. This also uncovered a bug in for/else loops, that wasn't teste before.

jedi/evaluate/cache.py

@@ -9,7 +9,7 @@ import inspect
 NO_DEFAULT = object()
 
 
-def memoize_default(default=None, evaluator_is_first_arg=False, second_arg_is_evaluator=False):
+def memoize_default(default=NO_DEFAULT, evaluator_is_first_arg=False, second_arg_is_evaluator=False):
     """ This is a typical memoization decorator, BUT there is one difference:
     To prevent recursion it sets defaults.