Return False when comparing a RowEvent to something else

The change to RowEvent code removing an isinstance check exposed
an issue when using the code in networking-ovn. Comparing a tuple
containing a RowEvent to the STOP_EVENT tuple calls:
row_event.__eq__(STOP_EVENT[0]) and STOP_EVENT[0] doesn't have a
key, so raises an exception.

Change-Id: Idf8edc7ced001c0fda545036cefbfefb918cb350

ovsdbapp/event.py

@@ -44,7 +44,10 @@ class RowEvent(object):
         return hash(self.key)
 
     def __eq__(self, other):
-        return self.key == other.key
+        try:
+            return self.key == other.key
+        except AttributeError:
+            return False
 
     def __ne__(self, other):
         return not self == other

ovsdbapp/tests/unit/test_event.py

@@ -0,0 +1,35 @@
+# Copyright (c) 2017 Red Hat, Inc.
+#
+#    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.
+
+
+from ovsdbapp import event
+from ovsdbapp.tests import base
+
+
+class TestEvent(event.RowEvent):
+    def __init__(self):
+        super(TestEvent, self).__init__(
+            (self.ROW_CREATE,), "FakeTable", (("col", "=", "val"),))
+
+    def run(self):
+        pass
+
+    def matches(self):
+        pass
+
+
+class TestRowEvent(base.TestCase):
+    def test_compare_stop_event(self):
+        r = TestEvent()
+        self.assertFalse((r, "fake", "fake", "fake") == event.STOP_EVENT)