Use isinstance and issubclass in partial ordering tests.

src/plone/folder/tests/test_partialordering.py

@@ -67,11 +67,7 @@ def runTableTests(self, action, tests):
             container, ordering = self.create()
             ids = set(container.objectIds())
             method = getattr(ordering, action)
-            if isinstance(rval, type):
-                # This means the return value is an Exception class.
-                # It is NOT an *instance* of an Exception class,
-                # so the following would not work:
-                # isinstance(rval, Exception)
+            if isinstance(rval, type) and issubclass(rval, Exception):
                 self.assertRaises(rval, method, *args)
             else:
                 self.assertEqual(method(*args), rval)