RLException: Invalid ＜param＞ tag: Cannot load command parameter [robot_description]: no such command

在ROS机器人开发实用案例分析中第五章搭建模拟机器人手臂里面的rrbot_rviz.lunch如下所示

运行会报出如下错误

RLException: Invalid  tag: Cannot load command parameter [robot_description]: no such command [['/opt/ros/noetic/share/xacro/xacro.py', '/home/lvrobot/ROSExample/src/ros_robotics/urdf/rrbot.xacro']]. 

Param xml is 
The traceback for the exception was written to the log file

其主要原因是在Noetic版本的ROS需要把

xacro.py

改为

xacro