add repr for event objects

When an event object gets dumped in a stack trace, because there
is no __repr__ of it, we don't get any details about what it was.
Add a __repr__ to all the event objects so that we can get this
information on a fail.

Change-Id: I9a62a4348871b748c53b7354ad1b821fe987127d

nova/tests/virt/test_events.py

@@ -0,0 +1,36 @@
+# All Rights Reserved.
+#
+# 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 time
+
+from nova import test
+from nova.virt import event
+
+
+class TestEvents(test.NoDBTestCase):
+
+    def test_event_repr(self):
+        t = time.time()
+        uuid = '1234'
+        lifecycle = event.EVENT_LIFECYCLE_RESUMED
+
+        e = event.Event(t)
+        self.assertEqual(str(e), "<Event: %s>" % t)
+
+        e = event.InstanceEvent(uuid, timestamp=t)
+        self.assertEqual(str(e), "<InstanceEvent: %s, %s>" % (t, uuid))
+
+        e = event.LifecycleEvent(uuid, lifecycle, timestamp=t)
+        self.assertEqual(str(e), "<LifecycleEvent: %s, %s => Resumed>" %
+                         (t, uuid))

nova/virt/event.py

@@ -56,6 +56,11 @@ class Event(object):
     def get_timestamp(self):
         return self.timestamp
 
+    def __repr__(self):
+        return "<%s: %s>" % (
+            self.__class__.__name__,
+            self.timestamp)
+
 
 class InstanceEvent(Event):
     """Base class for all instance events.
@@ -74,6 +79,12 @@ class InstanceEvent(Event):
     def get_instance_uuid(self):
         return self.uuid
 
+    def __repr__(self):
+        return "<%s: %s, %s>" % (
+            self.__class__.__name__,
+            self.timestamp,
+            self.uuid)
+
 
 class LifecycleEvent(InstanceEvent):
     """Class for instance lifecycle state change events.
@@ -95,3 +106,10 @@ class LifecycleEvent(InstanceEvent):
 
     def get_name(self):
         return NAMES.get(self.transition, _('Unknown'))
+
+    def __repr__(self):
+        return "<%s: %s, %s => %s>" % (
+            self.__class__.__name__,
+            self.timestamp,
+            self.uuid,
+            self.get_name())