roslaunch error

edit

I tried to run roslaunch excavator_gazebo gazebo.launch (using kinetic)

But I got this error :

xacro: Traditional processing is deprecated. Switch to --inorder processing!
To check for compatibility of your document, use option --check-order.
For more infos, see http://wiki.ros.org/xacro#Processing_Order

XML parsing error: unbound prefix: line 5, column 2
when processing file: /home/kmj/catkin_ws/src/excavator_description/urdf/excavator.xacro

Check that:

 - Your XML is well-formed
 - You have the xacro xmlns declaration: xmlns:xacro="http://www.ros.org/wiki/xacro"


Invalid <param> tag: Cannot load command parameter [description]: command [/opt/ros/kinetic/share/xacro/xacro.py '/home/kmj/catkin_ws/src/excavator_description/urdf/excavator.xacro'] returned with code [2]. 

Param xml is <param command="$(find xacro)/xacro.py '$(find excavator_description)/urdf/excavator.xacro'" name="description"/>
The traceback for the exception was written to the log file

I have no idea to solve this problem.

Do you know how to fix this?