Mark mqtt test exception as okay

The MQTT tests apparently start the mqtt client and allow it to
fail to connect, and then rely on a monkeypatched publish method
for further testing.  This causes a spurious connection failure
traceback in the logs.

If this happens in production, it's worth seeing the entire
traceback for debugging purposes, so mark this exception as expected
in tests.

This affects 8 unit tests.

Change-Id: I0a9b10f4dc1165b748e572a875dc4d6abbc3c563

tests/unit/test_connection.py

@@ -23,9 +23,15 @@ import sqlalchemy as sa
 
 import zuul
 from zuul.lib import yamlutil
-from tests.base import ZuulTestCase, FIXTURE_DIR, \
-    PostgresqlSchemaFixture, MySQLSchemaFixture, \
-    BaseTestCase, AnsibleZuulTestCase
+from tests.base import (
+    AnsibleZuulTestCase,
+    BaseTestCase,
+    FIXTURE_DIR,
+    MySQLSchemaFixture,
+    PostgresqlSchemaFixture,
+    ZuulTestCase,
+    okay_tracebacks,
+)
 
 
 class TestConnections(ZuulTestCase):
@@ -675,6 +681,7 @@ class TestMQTTConnection(ZuulTestCase):
     config_file = 'zuul-mqtt-driver.conf'
     tenant_config_file = 'config/mqtt-driver/main.yaml'
 
+    @okay_tracebacks('Connection refused')
     def test_mqtt_reporter(self):
         "Test the MQTT reporter"
         # Add a success result
@@ -749,8 +756,8 @@ class TestMQTTConnection(ZuulTestCase):
         self.assertEquals(dependent_test_job['dependencies'], ['test'])
         self.assertIn('test', dependent_test_job['job_dependencies'])
 
+    @okay_tracebacks('Connection refused')
     def test_mqtt_paused_job(self):
-
         A = self.fake_gerrit.addFakeChange("org/project", "master", "A")
         # Let the job being paused via the executor
         self.executor_server.returnData("test", A, {"zuul": {"pause": True}})
@@ -780,6 +787,7 @@ class TestMQTTConnection(ZuulTestCase):
         self.assertGreater(
             resume_event["event_time"], pause_event["event_time"])
 
+    @okay_tracebacks('Connection refused')
     def test_mqtt_retried_builds(self):
         self.executor_server.hold_jobs_in_build = True
         A = self.fake_gerrit.addFakeChange("org/project", "master", "A")
@@ -811,6 +819,7 @@ class TestMQTTConnection(ZuulTestCase):
         self.assertIn("execute_time", retry_build)
         self.assertIn("log_url", retry_build)
 
+    @okay_tracebacks('Connection refused')
     def test_mqtt_invalid_topic(self):
         in_repo_conf = textwrap.dedent(
             """
@@ -833,6 +842,7 @@ class TestMQTTConnection(ZuulTestCase):
         self.assertIn("topic component 'bad' is invalid", A.messages[0],
                       "A should report a syntax error")
 
+    @okay_tracebacks('Connection refused')
     def test_topic_replace_invalid_chars(self):
         # Test that special characters in the topic are replaced
         self.create_branch('org/project', 'weird#+')