Remove mox from nova/tests/unit/test_iptables_network.py

Replace stubs.Set() with mock.patch.object

Part of blueprint remove-mox-newton

Change-Id: Id2820d0908a302a05699de74d8e2a8f3bafb4c6d

nova/tests/unit/test_iptables_network.py

@@ -15,6 +15,7 @@
 #    under the License.
 """Unit Tests for network code."""
 
+import mock
 import six
 
 from nova.network import linux_net
@@ -107,11 +108,9 @@ class IptablesManagerTestCase(test.NoDBTestCase):
         for table in six.itervalues(self.manager.ipv6):
             table.dirty = False
 
-        def error_apply():
-            raise test.TestingException()
-
-        self.stubs.Set(self.manager, '_apply', error_apply)
-        self.manager.apply()
+        with mock.patch.object(self.manager, '_apply') as mock_apply:
+            self.manager.apply()
+            self.assertFalse(mock_apply.called)
 
     def test_filter_rules_are_wrapped(self):
         current_lines = self.sample_filter