Error when executing roslaunch baxter_gazebo baxter_world.launch

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Hello,

I am trying to simulate Baxter on Gazebo, I used the following instructions for the installation: http://sdk.rethinkrobotics.com/wiki/S... But after typing the command: roslaunch baxter_gazebo baxter_world.launch it gives me this error:

Invalid tag: Cannot load command parameter [robot_description]: command [/home/armand/ros_ws/src/xacro/xacro.py --inorder /home/armand/ros_ws/src/baxter_common/baxter_description/urdf/baxter.urdf.xacro gazebo:=true] returned with code [2].

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

Does anyone have any idea how to make it work?

PS: I am using ROS indigo on Ubuntu 14.04