How launch a python script with roslaunch

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Hello there,

I am trying to launch a script called mtnode.py from a package called xsens_drive. When I use rosrun it works perfectly, however i have difficulty to launch it with roslaunch. This is the syntax that I use:

  <node pkg="xsens_drive" name="mtnode.py" type="mtnode.py" output="screen">
        <param name="frame_id" value="base_link" />
  </node>

and this is the warning and error form the roslaunch:

WARNING: WARN: illegal <node> name 'mtnode.py'.
http://ros.org/wiki/Names
This will likely cause problems with other ROS tools.
Node xml is <node name="mtnode.py" output="screen" pkg="xsens_drive" type="mtnode.py">
        <param name="frame_id" value="base_link"/>
  </node>

and the error:

ERROR: cannot launch node of type [xsens_drive/mtnode.py]: xsens_drive
ROS path [0]=/opt/ros/indigo/share/ros
ROS path [1]=/home/sherpa/catkin_ws/src
ROS path [2]=/opt/ros/indigo/share
ROS path [3]=/opt/ros/indigo/stacks

I tried different combination of name and type without .py with no luck, I am using ros indigo

Thanks in advance