my_activity.py: Parse rietveld dates without milliseconds.

my_activity.py

Index: my_activity.py
diff --git a/my_activity.py b/my_activity.py
index 33694eba48ef50c364159257385cce52393c9083..48aeaea7b48b71a5277f9a138743779b9b918956 100755
--- a/my_activity.py
+++ b/my_activity.py
@@ -191,7 +191,12 @@ def datetime_from_gerrit(date_string):
 
 
 def datetime_from_rietveld(date_string):
-  return datetime.strptime(date_string, '%Y-%m-%d %H:%M:%S.%f')
+  try:
+    return datetime.strptime(date_string, '%Y-%m-%d %H:%M:%S.%f')
+  except ValueError:
+    # Sometimes rietveld returns a value without the milliseconds part, so we
+    # attempt to parse those cases as well.
+    return datetime.strptime(date_string, '%Y-%m-%d %H:%M:%S')
 
 
 def datetime_from_google_code(date_string):