queue: Extract get_remaining_queue_size method.

zerver/worker/queue_processors.py

@@ -207,6 +207,15 @@ class QueueProcessingWorker(ABC):
                 )
             os.rename(tmp_fn, fn)
 
+    def get_remaining_queue_size(self) -> int:
+        if self.q is not None:
+            return self.q.queue_size()
+        else:
+            # This is a special case that will happen if we're operating without
+            # using RabbitMQ (e.g. in tests). In that case there's no queuing to speak of
+            # and the only reasonable size to return is 0.
+            return 0
+
     @abstractmethod
     def consume(self, data: Dict[str, Any]) -> None:
         pass
@@ -228,11 +237,7 @@ class QueueProcessingWorker(ABC):
             if consume_time_seconds is not None:
                 self.recent_consume_times.append((len(events), consume_time_seconds))
 
-            if self.q is not None:
-                remaining_queue_size = self.q.queue_size()
-            else:
-                remaining_queue_size = 0
-
+            remaining_queue_size = self.get_remaining_queue_size()
             if remaining_queue_size == 0:
                 self.queue_last_emptied_timestamp = time.time()
                 self.consumed_since_last_emptied = 0