How to load urdf.xacro in ros-noetic?

edit

I trid two ways(way1 and way2) to load urdf ,it's all ok in ros-kinetic(ubuntn16.04);but the ways all failed in ros-noetic(ubuntu20.04).What can I do to solve this problem?

when test in ros-noetic,I get:

ylh@ylh:~$ roslaunch test test.launch 

... logging to /home/ylh/.ros/log/151c452e-a09c-11ea-9172-8f7723f9d611/roslaunch-ylh-25551.log
Checking log directory for disk usage. This may take a while.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

No such file or directory: /home/ylh/catkin_ws/src/arobot_ws/test/urdf/test.urdf.xacro [Errno 2] No such file or directory: '/home/ylh/catkin_ws/src/arobot_ws/test/urdf/test.urdf.xacro'
RLException: Invalid <param> tag: Cannot load command parameter [robot_description]: command [['/opt/ros/noetic/lib/xacro/xacro', '/home/ylh/catkin_ws/src/arobot_ws/test/urdf/test.urdf.xacro']] returned with code [2]. 

Param xml is 

     (way1)  param name="robot_description" command="$(find xacro)/xacro '$(find test)/urdf/test.urdf.xacro'"

The traceback for the exception was written to the log file


ylh@ylh:~$ roslaunch test test.launch 

... logging to /home/ylh/.ros/log/3203c572-a09c-11ea-9172-8f7723f9d611/roslaunch-ylh-25605.log
Checking log directory for disk usage. This may take a while.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

cat: /home/ylh/catkin_ws/src/arobot_ws/test/urdf/test.urdf.xacro: No such file or directory
RLException: Invalid <param> tag: Cannot load command parameter [robot_description]: command [['cat', '/home/ylh/catkin_ws/src/arobot_ws/test/urdf/test.urdf.xacro']] returned with code [1]. 

Param xml is 

      (way2)  param name="robot_description" command="cat '$(find test)/urdf/test.urdf.xacro'"

The traceback for the exception was written to the log file

ylh@ylh:~$

test.urdf.xacro:

<robot xmlns:xacro = "http://www.ros.org/wiki/xacro"  name="test">

 <link name="base_link">
    <visual>
       <geometry>
          <box size="1 1 0.1"/>
       </geometry>
   </visual>
   <collision>
        <geometry>
          <box size="1 1 0.1"/>
        </geometry>
   </collision>
    <inertial>
       <mass value="40" />
       <origin xyz="0 0 0" rpy="0 0 0"/>
       <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1" />
     </inertial>
 </link>

 <joint name="wheel_to_base_link" type="continuous">
     <parent link="base_link"/>
     <child link="board"/>
     <origin xyz="0 0 -0.4" rpy="0 0 0"/>
     <axis xyz="0 1 0" rpy="0 0 0" />
 </joint>
 <link name="board">
    <visual>
       <geometry>
          <cylinder length="0.1" radius="0.2"/>
       </geometry>
     <origin rpy="1.5707 0 0" xyz="0 0 0"/>
   </visual>
   <collision>
        <geometry>
          <cylinder length="0.1" radius="0.2"/>
        </geometry>
    <origin rpy="1.5707 0 0" xyz="0 0 0"/>
   </collision>
    <inertial>
       <mass value="1" />
       <origin xyz="0 0 0" rpy="0 0 0"/>
       <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1" />
     </inertial>
 </link> 

< /robot >

What can I do to solve this ... (more)