Forbid new legacy notification event_type

As we agreed on the Mitaka midcycle no new legacy notification
event_type are allowed in Nova and every new notification shall
use the versioned notification framework.

This patch adds a validation step into the legacy notification
sending call chain. It checks the event_type against a whitelist.
During unit and functional testing an exception is raised if the
event_type is not known and therefore forbiden. This check is not
100% foolproof as it only detects the new event_type if there is
a test that triggers the sending of it and this check is not capable
of detecting such event_types if the test directly mocks
nova.rpc.get_notifier.

During normal operation a WARNING is logged so that a logstash query
can be set up to detect the rest of the cases.

Change-Id: Ia6600868aa7b3a22cb8c020503f49dce6a4c2c2b

nova/test.py

@@ -244,6 +244,8 @@ class TestCase(testtools.TestCase):
 
         openstack_driver.DRIVER_CACHE = {}
 
+        self.useFixture(nova_fixtures.ForbidNewLegacyNotificationFixture())
+
     def _restore_obj_registry(self):
         objects_base.NovaObjectRegistry._registry._obj_classes = \
                 self._base_test_obj_backup

nova/tests/fixtures.py

@@ -524,3 +524,26 @@ class EngineFacadeFixture(fixtures.Fixture):
 
     def cleanup(self):
         self._ctx_manager._root_factory = self._existing_factory
+
+
+class ForbidNewLegacyNotificationFixture(fixtures.Fixture):
+    """Make sure the test fails if new legacy notification is added"""
+    def __init__(self):
+        super(ForbidNewLegacyNotificationFixture, self).__init__()
+        self.notifier = rpc.LegacyValidatingNotifier
+
+    def setUp(self):
+        super(ForbidNewLegacyNotificationFixture, self).setUp()
+        self.notifier.fatal = True
+
+        # allow the special test value used in
+        # nova.tests.unit.test_notifications.NotificationsTestCase
+        self.notifier.allowed_legacy_notification_event_types.append(
+                '_decorated_function')
+
+        self.addCleanup(self.cleanup)
+
+    def cleanup(self):
+        self.notifier.fatal = False
+        self.notifier.allowed_legacy_notification_event_types.remove(
+                '_decorated_function')