Merge pull request vitessio#4224 from michael-berlin/caller_id

py: Change CallerID to have a useful repr.

py/vtdb/vtgate_client.py

@@ -1,11 +1,11 @@
 # Copyright 2017 Google 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.
@@ -71,6 +71,9 @@ def __init__(self, principal=None, component=None, subcomponent=None):
     self.component = component
     self.subcomponent = subcomponent
 
+  def __repr__(self):
+    return repr((self.principal, self.component, self.subcomponent))
+
 
 class VTGateClient(object):
   """VTGateClient is the interface for the vtgate client implementations.