Fixed #19617 -- Refactored Form metaclasses to support more inheritance scenarios.

Thanks apollo13, funkybob and mjtamlyn for the reviews.

1 files changed, 8 insertions, 4 deletions

diff --git a/django/forms/widgets.py b/django/forms/widgets.py
index 67befcfbe0..e80584a5c7 100644
--- a/django/forms/widgets.py
+++ b/django/forms/widgets.py
@@ -131,12 +131,16 @@ def media_property(cls):
     return property(_media)
 
 class MediaDefiningClass(type):
-    "Metaclass for classes that can have media definitions"
-    def __new__(cls, name, bases, attrs):
-        new_class = super(MediaDefiningClass, cls).__new__(cls, name, bases,
-                                                           attrs)
+    """
+    Metaclass for classes that can have media definitions.
+    """
+    def __new__(mcs, name, bases, attrs):
+        new_class = (super(MediaDefiningClass, mcs)
+            .__new__(mcs, name, bases, attrs))
+
         if 'media' not in attrs:
             new_class.media = media_property(new_class)
+
         return new_class
 
 @python_2_unicode_compatible