Implemented audit.update notification

In this changeset, I implemented the sending of update notifications
whenever an audit is modified.

Change-Id: I5ccc2516ce896ae7d4ef542b133e8f052eaed602
Partially-Implements: blueprint audit-versioned-notifications-api

watcher/notifications/exception.py

@@ -0,0 +1,53 @@
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import inspect
+
+import six
+
+from watcher.notifications import base as notificationbase
+from watcher.objects import base as base
+from watcher.objects import fields as wfields
+
+
+@base.WatcherObjectRegistry.register_notification
+class ExceptionPayload(notificationbase.NotificationPayloadBase):
+    # Version 1.0: Initial version
+    VERSION = '1.0'
+    fields = {
+        'module_name': wfields.StringField(),
+        'function_name': wfields.StringField(),
+        'exception': wfields.StringField(),
+        'exception_message': wfields.StringField()
+    }
+
+    @classmethod
+    def from_exception(cls, fault):
+        trace = inspect.trace()[-1]
+        # TODO(gibi): apply strutils.mask_password on exception_message and
+        # consider emitting the exception_message only if the safe flag is
+        # true in the exception like in the REST API
+        return cls(
+            function_name=trace[3],
+            module_name=inspect.getmodule(trace[0]).__name__,
+            exception=fault.__class__.__name__,
+            exception_message=six.text_type(fault))
+
+
+@notificationbase.notification_sample('infra-optim-exception.json')
+@base.WatcherObjectRegistry.register_notification
+class ExceptionNotification(notificationbase.NotificationBase):
+    # Version 1.0: Initial version
+    VERSION = '1.0'
+    fields = {
+        'payload': wfields.ObjectField('ExceptionPayload')
+    }