roslaunch px4 multi_uav_mavros_sitl_sdf.launch报错

在试图运行multi_uav_mavros_sitl_sdf.launch时报错：

while processing /home/sp/src/Firmware/launch/single_vehicle_spawn_sdf.launch:
Invalid <param> tag: Cannot load command parameter [model_description]: no such command [xmlstarlet ed -d '//plugin[@name="mavlink_interface"]/mavlink_tcp_port' -s '//plugin[@name="mavlink_interface"]' -t elem -n mavlink_tcp_port -v 4560 /home/sp/src/Firmware/Tools/sitl_gazebo/models/plane/plane.sdf].

Param xml is <param command="$(arg cmd)" name="model_description"/>
The traceback for the exception was written to the log file

其实本来是很简单的错误，就是没想明白： no such command

就是没有安装xmlstarlet，sudo apt install xmlstarlet 就好了