keep UserDict an old-style class

Be generous in abc.py to allow this.

1 files changed, 3 insertions, 1 deletions

diff --git a/Lib/abc.py b/Lib/abc.py
index c37ed8f..515ba08 100644
--- a/Lib/abc.py
+++ b/Lib/abc.py
@@ -3,6 +3,8 @@
 
 """Abstract Base Classes (ABCs) according to PEP 3119."""
 
+import types
+
 
 # Instance of old-style class
 class _C: pass
@@ -101,7 +103,7 @@ class ABCMeta(type):
 
     def register(cls, subclass):
         """Register a virtual subclass of an ABC."""
-        if not isinstance(subclass, type):
+        if not isinstance(subclass, (type, types.ClassType)):
             raise TypeError("Can only register classes")
         if issubclass(subclass, cls):
             return  # Already a subclass