Use mock for a bad HTTP call in unit tests

Depending on the test environment, in test_retry_policy and
test_task_defaults_on_error unit tests, the bad URL in the workbook/workflow
returned an unexpected response. These are poorly written unit tests as they
try to make actual HTTP call to the bad URLs. This patch mocks the HTTP
calls instead.

Change-Id: Ib155bfe8040f05fe05f9665d3e75f98e205bdd6b
Closes-Bug: bug/1641209

mistral/tests/unit/engine/test_policies.py

@@ -14,6 +14,7 @@
 
 import mock
 from oslo_config import cfg
+import requests
 
 from mistral.actions import std_actions
 from mistral.db.v2 import api as db_api
@@ -512,6 +513,11 @@ class PoliciesTest(base.EngineTestCase):
         # Need to create a better test.
         # self.assertEqual(2, task_ex.in_context['wait_after'])
 
+    @mock.patch.object(
+        requests,
+        'request',
+        mock.MagicMock(side_effect=Exception())
+    )
     def test_retry_policy(self):
         wb_service.create_workbook_v2(RETRY_WB)
 

mistral/tests/unit/engine/test_task_defaults.py

@@ -13,7 +13,9 @@
 #    limitations under the License.
 
 import datetime as dt
+import mock
 from oslo_config import cfg
+import requests
 
 from mistral.db.v2 import api as db_api
 from mistral.services import scheduler
@@ -28,6 +30,12 @@ cfg.CONF.set_default('auth_enable', False, group='pecan')
 
 
 class TaskDefaultsDirectWorkflowEngineTest(base.EngineTestCase):
+
+    @mock.patch.object(
+        requests,
+        'request',
+        mock.MagicMock(side_effect=Exception())
+    )
     def test_task_defaults_on_error(self):
         wf_text = """---
         version: '2.0'