Fix coverage job for Python 3

* add coverage check job to Zuul
* migrate to stestr as described in PTI [1]
* unmock OffsetOutOfRangeError to correctly recognize it as Exception
and not a mock. Otherwise TypeError exception is thrown [2].

[1] https://governance.openstack.org/tc/reference/pti/python.html#coverage-jobs
[2] http://logs.openstack.org/60/606660/2/check/openstack-tox-cover/b3c1492/testr_results.html.gz

Change-Id: Idcb8b11778ce02596c1c02417ee6c88a33c7da03
Story: 2003240
Task: 26900

.zuul.yaml

@@ -1,5 +1,6 @@
 - project:
     templates:
+      - openstack-cover-jobs
       - openstack-python-jobs
       - openstack-python35-jobs
       - openstack-python36-jobs

monasca_common/tests/test_kafka.py

@@ -16,6 +16,7 @@ from oslotest import base
 
 from monasca_common.kafka import consumer
 from monasca_common.kafka import producer
+from monasca_common.kafka_lib import common as kafka_common
 
 
 FAKE_KAFKA_URL = "kafka_url"
@@ -104,6 +105,7 @@ class TestKafkaConsumer(base.BaseTestCase):
 
         self.mock_kafka_client = self.kafka_client_patcher.start()
         self.mock_kafka_common = self.kafka_common_patcher.start()
+        self.mock_kafka_common.OffsetOutOfRangeError = kafka_common.OffsetOutOfRangeError
         self.mock_kafka_consumer = self.kafka_consumer_patcher.start()
         self.kazoo_patcher.start()
 

tox.ini

@@ -41,11 +41,14 @@ commands =
 
 [testenv:cover]
 basepython = python2.7
+setenv =
+    PYTHON=coverage run --source monasca_common --parallel-mode
 commands =
-  {[testenv]commands}
-  coverage erase
-  python setup.py test --coverage --testr-args='{posargs}' --coverage-package-name=monasca_common
-  coverage report
+    coverage erase
+    stestr run '{posargs}'
+    coverage combine
+    coverage html -d cover
+    coverage xml -o cover/coverage.xml
 
 [testenv:debug]
 basepython = python3