Python string format (ros-navigation#2466)

* Convert to python format strings for readability

* Merge concatenated strings

* Revert converting generated files

* Single quotes for consistency

* Just print the exception

nav2_bringup/bringup/launch/multi_tb3_simulation_launch.py

@@ -123,7 +123,7 @@ def generate_launch_description():
     # Define commands for launching the navigation instances
     nav_instances_cmds = []
     for robot in robots:
-        params_file = LaunchConfiguration(robot['name'] + '_params_file')
+        params_file = LaunchConfiguration(f"{robot['name']}_params_file")
 
         group = GroupAction([
             IncludeLaunchDescription(

nav2_bringup/nav2_gazebo_spawner/nav2_gazebo_spawner/nav2_gazebo_spawner.py

@@ -67,7 +67,7 @@ def main():
     if args.turtlebot_type is not None:
         sdf_file_path = os.path.join(
             get_package_share_directory('turtlebot3_gazebo'), 'models',
-            'turtlebot3_{}'.format(args.turtlebot_type), 'model.sdf')
+            f'turtlebot3_{args.turtlebot_type}', 'model.sdf')
     else:
         sdf_file_path = args.sdf
 
@@ -86,7 +86,7 @@ def main():
     if args.robot_namespace:
         ros_params = plugin.find('ros')
         ros_tf_remap = ET.SubElement(ros_params, 'remapping')
-        ros_tf_remap.text = '/tf:=/' + args.robot_namespace + '/tf'
+        ros_tf_remap.text = f'/tf:=/{args.robot_namespace}/tf'
 
     # Set data for request
     request = SpawnEntity.Request()
@@ -101,10 +101,10 @@ def main():
     future = client.call_async(request)
     rclpy.spin_until_future_complete(node, future, timeout_sec=args.timeout)
     if future.result() is not None:
-        print('response: %r' % future.result())
+        print(f'response: {future.result()!r}')
     else:
         raise RuntimeError(
-            'exception while calling service: %r' % future.exception())
+            f'exception while calling service: {future.exception()!r}')
 
     node.get_logger().info('Done! Shutting down node.')
     node.destroy_node()