Launch file doesn't work after xacro update

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Hello there,

After updating to version 1.9.4 of the ros-indigo-xacro package, one of my launch files doesn't work anymore, and I can't figure out why. The error mesages I get are the following:

Traceback (most recent call last):
  File "/opt/ros/indigo/share/xacro/xacro.py", line 60, in <module>
    xacro.main()
  File "/opt/ros/indigo/lib/python2.7/dist-packages/xacro/__init__.py", line 706, in main
    open_output(output_filename).write(doc.toprettyxml(indent='  '))
UnicodeEncodeError: 'ascii' codec can't encode character u'\xb7' in position 1960: ordinal not in range(128)
while processing /home/daniel/catkin_ws/src/rotors_simulator/rotors_gazebo/launch/spawn_mav.launch:
Invalid <param> tag: Cannot load command parameter [robot_description]: command [     /opt/ros/indigo/share/xacro/xacro.py '/home/daniel/catkin_ws/src/rotors_simulator/rotors_description/urdf/firefly_base.xacro'     enable_logging:=false     enable_ground_truth:=true     log_file:=firefly     mav_name:=firefly] returned with code [1]. 

Param xml is <param command="     $(find xacro)/xacro.py '$(arg model)'     enable_logging:=$(arg enable_logging)     enable_ground_truth:=$(arg enable_ground_truth)     log_file:=$(arg log_file)     mav_name:=$(arg mav_name)" name="robot_description"/>
The traceback for the exception was written to the log file

The launch file is this:

<?xml version="1.0" ?>

<launch>
  <arg name="mav_name" />
  <arg name="model" default="$(find rotors_description)/urdf/$(arg mav_name)_base.xacro"/>
  <arg name="tf_prefix" default="$(optenv ROS_NAMESPACE)"/>
  <arg name="x" default="0.0"/>
  <arg name="y" default="0.0"/>
  <arg name="z" default="0.1"/>
  <arg name="enable_logging" default="false"/>
  <arg name="enable_ground_truth" default="true"/>
  <arg name="log_file" default="$(arg mav_name)"/>

  <!-- send the robot XML to param server -->
  <param name="robot_description" command="
    $(find xacro)/xacro.py '$(arg model)'
    enable_logging:=$(arg enable_logging)
    enable_ground_truth:=$(arg enable_ground_truth)
    log_file:=$(arg log_file)
    mav_name:=$(arg mav_name)"
  />
  <param name="tf_prefix" type="string" value="$(arg tf_prefix)" />

  <!-- push robot_description to factory and spawn robot in gazebo -->
  <node name="spawn_$(arg mav_name)" pkg="gazebo_ros" type="spawn_model"
   args="-param robot_description
         -urdf
         -x $(arg x)
         -y $(arg y)
         -z $(arg z)
         -model $(arg mav_name)"
   respawn="false" output="screen">
  </node>
</launch>

Any help would be greatly appreciated!

Cheers, Daniel