Add importing modules instead of classes

This patch removes import of classes and replaces them with import of modules.

Change-Id: Id2502cf96ac7227cf1036cd54a74f3d7acd83479
Closes-Bug: #1594434

watcher/tests/objects/test_action_plan.py

@@ -14,7 +14,7 @@
 #    under the License.
 
 import mock
-from testtools.matchers import HasLength
+from testtools import matchers
 
 from watcher.common import exception
 # from watcher.common import utils as w_utils
@@ -58,7 +58,7 @@ class TestActionPlanObject(base.DbTestCase):
             mock_get_list.return_value = [self.fake_action_plan]
             action_plans = objects.ActionPlan.list(self.context)
             self.assertEqual(1, mock_get_list.call_count)
-            self.assertThat(action_plans, HasLength(1))
+            self.assertThat(action_plans, matchers.HasLength(1))
             self.assertIsInstance(action_plans[0], objects.ActionPlan)
             self.assertEqual(self.context, action_plans[0]._context)