stats: Make get_timer return a stub object if Graphite disabled.

This saves us from having to do explicit checks for whether or
not the timer exists everywhere we use them.

r2/r2/lib/stats.py

@@ -85,7 +85,7 @@ class Stats:
         if self.connection:
             return self.statsd.timer.Timer(name, self.connection)
         else:
-            return None
+            return utils.SimpleSillyStub()
 
     def transact(self, action, service_time_sec):
         timer = self.get_timer('service_time')

r2/r2/lib/utils/utils.py

@@ -1310,6 +1310,17 @@ class Bomb(object):
     def __repr__(cls):
         raise Hell()
 
+class SimpleSillyStub(object):
+    """A simple stub object that does nothing when you call its methods."""
+    def __nonzero__(self):
+        return False
+
+    def __getattr__(self, name):
+        return self.stub
+
+    def stub(self, *args, **kwargs):
+        pass
+
 def strordict_fullname(item, key='fullname'):
     """Sometimes we migrate AMQP queues from simple strings to pickled
     dictionaries. During the migratory period there may be items in