memoize problems with defaults in combination with raised exceptions

jedi/evaluate/cache.py

@@ -4,6 +4,8 @@
 - ``CachedMetaClass`` uses ``memoize_default`` to do the same with classes.
 """
 
+NO_DEFAULT = object()
+
 
 def memoize_default(default=None, evaluator_is_first_arg=False, second_arg_is_evaluator=False):
     """ This is a typical memoization decorator, BUT there is one difference:
@@ -32,7 +34,8 @@ def memoize_default(default=None, evaluator_is_first_arg=False, second_arg_is_ev
             if key in memo:
                 return memo[key]
             else:
-                memo[key] = default
+                if default is not NO_DEFAULT:
+                    memo[key] = default
                 rv = function(obj, *args, **kwargs)
                 memo[key] = rv
                 return rv