make version of ts_mon compatible with appengine

infra_libs/ts_mon/interface.py

Index: infra_libs/ts_mon/interface.py
diff --git a/infra_libs/ts_mon/interface.py b/infra_libs/ts_mon/interface.py
index e24bf14d120309f21c77e967f35908a3c5d31741..f5af177b5ae6d93a27341a91b04615a269b4fbb1 100644
--- a/infra_libs/ts_mon/interface.py
+++ b/infra_libs/ts_mon/interface.py
@@ -39,7 +39,7 @@ import time
 
 from monacq.proto import metrics_pb2
 
-from infra_libs.ts_mon import errors
+from infra_libs.ts_mon.common import errors
 
 # The maximum number of MetricsData messages to include in each HTTP request.
 # MetricsCollections larger than this will be split into multiple requests.
@@ -111,19 +111,20 @@ def flush():
 def register(metric):
   """Adds the metric to the list of metrics sent by flush().
 
-  This is called automatically by Metric's constructor - you don't need to call
-  it manually.
+  This is called automatically by Metric's constructor.
   """
   # If someone is registering the same metric object twice, that's okay, but
   # registering two different metric objects with the same metric name is not.
-  if metric in state.metrics:
-    return
+  for m in state.metrics:
+    if metric == m:
+      state.metrics.remove(m)
+      state.metrics.add(metric)
+      return
   if any([metric._name == m._name for m in state.metrics]):
     raise errors.MonitoringDuplicateRegistrationError(metric._name)
 
   state.metrics.add(metric)
 
-
 def unregister(metric):
   """Removes the metric from the list of metrics sent by flush()."""
   state.metrics.remove(metric)