xarm问题

1.问题描述

xacro: in-order processing became default in ROS Melodic. You can drop the option.
substitution args not supported:  No module named 'rospkg'
when processing file: /root/catkin_ws/src/xarm_ros/xarm_description/urdf/xarm7_robot.urdf.xacro
RLException: while processing /root/catkin_ws/src/xarm_ros/xarm_description/launch/xarm7_upload.launch:
Invalid  tag: Cannot load command parameter [robot_description]: command [['/opt/ros/noetic/lib/xacro/xacro', '--inorder', '/root/catkin_ws/src/xarm_ros/xarm_description/urdf/xarm7_robot.urdf.xacro', 'limited:=True']] returned with code [2].

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

2.解决办法

安装rospkg

pip install rospkg