Index: Python/ceval.c
===================================================================
--- Python/ceval.c	(revision 61449)
+++ Python/ceval.c	(working copy)
@@ -3161,6 +3161,13 @@
 			     type->ob_type->tp_name);
 		goto raise_error;
 	}
+	assert(PyExceptionClass_Check(type));
+	if (Py_Py3kWarningFlag && 
+	    PyClass_Check(type) &&
+            PyErr_Warn(PyExc_DeprecationWarning,
+		       "exceptions must derive from BaseException in 3.x"))
+		goto raise_error;
+
 	PyErr_Restore(type, value, tb);
 	if (tb == NULL)
 		return WHY_EXCEPTION;