use single quote

squizz617 · squizz617 · commit 5b8faab8b1f9 · 2022-02-04T10:36:14.000-05:00
diff --git a/rclpy/rclpy/time_source.py b/rclpy/rclpy/time_source.py
@@ -124,7 +124,7 @@ def clock_callback(self, msg):
 
     def _on_parameter_event(self, parameter_list):
         successful = True
-        reason = ""
+        reason = ''
 
         for parameter in parameter_list:
             if parameter.name == USE_SIM_TIME_NAME:
