raise a clear TypeError when trying to register a non-class
diff --git a/Lib/test/test_abc.py b/Lib/test/test_abc.py
index 529f3e6..31f1986 100644
--- a/Lib/test/test_abc.py
+++ b/Lib/test/test_abc.py
@@ -149,6 +149,12 @@
         self.assertRaises(RuntimeError, C.register, A)  # cycles not allowed
         C.register(B)  # ok
 
+    def test_register_non_class(self):
+        class A(object):
+            __metaclass__ = abc.ABCMeta
+        self.assertRaisesRegexp(TypeError, "Can only register classes",
+                                A.register, 4)
+
     def test_registration_transitiveness(self):
         class A:
             __metaclass__ = abc.ABCMeta