Active a unit test in comon/test_validators

In a word, the reason why type is None is that JSONSchema
checker doesn't return the unified form when the outmost layer
of JSONSchema doesn't pass the examination.

So, we can use assertIn instead.

Change-Id: I49a2879ce249d83ee7ab36f1e0a67fe887aa4738
Closes-bug: #1531841

barbican/tests/common/test_validators.py

@@ -664,14 +664,13 @@ class WhenTestingContainerValidator(utils.BaseTestCase):
     def test_should_raise_no_type(self):
         del self.container_req['type']
 
-        self.assertRaises(
+        exception = self.assertRaises(
             excep.InvalidObject,
             self.validator.validate,
             self.container_req,
         )
 
-        # TODO(hgedikli): figure out why invalid_property is null here
-        # self.assertEqual('type', e.exception.invalid_property)
+        self.assertIn('type', exception.message)
 
     def test_should_raise_empty_type(self):
         self.container_req['type'] = ''