use new style classes

Author: jreback

pandas/core/dtypes/dtypes.py

@@ -9,7 +9,7 @@
 from .base import ExtensionDtype, _DtypeOpsMixin
 
 
-class Registry:
+class Registry(object):
     """ class to register our dtypes for inference
 
     We can directly construct dtypes in pandas_dtypes if they are