Gazebo: Invalid <param> tag: Cannot load command parameter [robot_description]

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My original package worked well. But after I added a mavlink_interface_macro to my xacro file of the model, I got the following error:

when processing file: /home/u23/WorkSpace/03.fixedwing_sim_pix/04.Firmware/Firmware/Tools/sitl_gazebo/models/techpod/techpod_base.xacro
unknown macro name: xacro:mavlink_interface_macro

when processing file: /home/u23/WorkSpace/03.fixedwing_sim_pix/04.Firmware/Firmware/Tools/sitl_gazebo/models/techpod/techpod_base.xacro

while processing /home/u23/WorkSpace/03.fixedwing_sim_pix/04.Firmware/Firmware/launch/spawn_fixed_wing.launch:

Invalid <param> tag: Cannot load command parameter [robot_description]: command [     /opt/ros/jade/share/xacro/xacro.py '/home/u23/WorkSpace/03.fixedwing_sim_pix/04.Firmware/Firmware/Tools/sitl_gazebo/models/techpod/techpod_base.xacro'     enable_logging:=false     enable_ground_truth:=true     log_file:=techpod     wait_to_record_bag:=false     uav_name:=techpod     namespace:=techpod] returned with code [2]. 

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:=$(arg log_file)     wait_to_record_bag:=$(arg wait_to_record_bag)     uav_name:=$(arg uav_name)     namespace:=$(arg namespace)" name="robot_description"/>

The traceback for the exception was written to the log file

I checked the xacro file to make sure the mavlink_interface_macro was defined and added in the corrected way. Before I added it the param [robot_description] was also successfully loaded.

I tried some ways I saw from other examples, like:

rosrun xacro xacro my_model_name.xacro > /tmp/old.xml

I got:

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
redefining global property: pi
when processing file: techpod_base.xacro
Undefined substitution argument namespace 
when evaluating expression 'namespace'
when processing file: techpod_base.xacro

However the expression namespace works well when quoted in other macro. I am confused of the relations between the two errors. I checked the log file, which shows:

Invalid <param> tag: Cannot load command parameter [robot_description]: command [     /opt/ros/jade/share/xacro/xacro.py '/home/u23/WorkSpace/03.fixedwing_sim_pix/04.Firmware/Firmware/Tools/sitl_gazebo/models/techpod/techpod_base.xacro'     enable_logging:=false     enable_ground_truth:=true     log_file:=techpod     wait_to_record_bag:=false     uav_name:=techpod     namespace:=techpod] returned with code [2]. 
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:=$(arg log_file)     wait_to_record_bag:=$(arg wait_to_record_bag)     uav_name:=$(arg uav_name)     namespace:=$(arg namespace)" name="robot_description"/>
[roslaunch][ERROR] 2017-03-11 16:06:37,576: The traceback for the exception was written to the log file
[roslaunch][ERROR] 2017-03-11 16:06:37,577: Traceback (most recent call last):
 File "/opt/ros/jade/lib/python2.7/dist-packages/roslaunch/__init__.py", line 307, in main
    p.start()
 File "/opt/ros/jade/lib/python2.7/dist-packages/roslaunch/parent.py", line 268, in start
    self._start_infrastructure()
 File "/opt/ros/jade/lib/python2.7/dist-packages/roslaunch/parent.py", line 217, in _start_infrastructure
    self._load_config()
File "/opt/ros/jade/lib/python2.7/dist-packages/roslaunch/parent.py", line 132, in _load_config
    roslaunch_strs=self.roslaunch_strs, verbose=self.verbose)
File "/opt/ros/jade/lib/python2.7/dist-packages/roslaunch/config.py", line 453, in load_config_default
                raise RLException(e)
            `RLException: while processing` 
             /home/u23/WorkSpace/03.fixedwing_sim_pix/04.Firmware/Firmware/launch/spawn_fixed_wing ...