xacro parsing failed

[huqin-RM]

run ros2 launch moveit2_tutorials demo.launch.py rviz_tutorial:=true

result：

[INFO] [launch]: All log files can be found below /home/hu/.ros/log/2023-09-14-14-58-02-932993-hu-ASUS-TUF-Gaming-F15-FX507ZM-FX507ZM-195312
[INFO] [launch]: Default logging verbosity is set to INFO
/home/hu/moveit2/install/moveit_resources_panda_moveit_config/share/moveit_resources_panda_moveit_config
/home/hu/moveit2/install/moveit_resources_panda_moveit_config/share/moveit_resources_panda_moveit_config/config/panda.urdf.xacro
Task exception was never retrieved
future: <Task finished name='Task-2' coro=<LaunchService._process_one_event() done, defined at /opt/ros/foxy/lib/python3.8/site-packages/launch/launch_service.py:226> exception=InvalidLaunchFileError('py')>
Traceback (most recent call last):
File "/opt/ros/foxy/lib/python3.8/site-packages/launch/launch_description_sources/any_launch_file_utilities.py", line 53, in get_launch_description_from_any_launch_file
return loader(launch_file_path)
File "/opt/ros/foxy/lib/python3.8/site-packages/launch/launch_description_sources/python_launch_file_utilities.py", line 68, in get_launch_description_from_python_launch_file
return getattr(launch_file_module, 'generate_launch_description')()
File "/home/hu/moveit2/install/moveit2_tutorials/share/moveit2_tutorials/launch/demo.launch.py", line 48, in generate_launch_description
robot_description_config = xacro.process_file(
File "/home/hu/.local/lib/python3.8/site-packages/xacro/init.py", line 1020, in process_file
process_doc(doc, **kwargs)
File "/home/hu/.local/lib/python3.8/site-packages/xacro/init.py", line 967, in process_doc
eval_all(doc.documentElement, macros, symbols)
File "/home/hu/.local/lib/python3.8/site-packages/xacro/init.py", line 852, in eval_all
if name not in substitution_args_context['arg']:
KeyError: 'arg'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/opt/ros/foxy/lib/python3.8/site-packages/launch/launch_service.py", line 228, in _process_one_event
await self.__process_event(next_event)
File "/opt/ros/foxy/lib/python3.8/site-packages/launch/launch_service.py", line 248, in __process_event
visit_all_entities_and_collect_futures(entity, self.__context))
File "/opt/ros/foxy/lib/python3.8/site-packages/launch/utilities/visit_all_entities_and_collect_futures_impl.py", line 45, in visit_all_entities_and_collect_futures
futures_to_return += visit_all_entities_and_collect_futures(sub_entity, context)
File "/opt/ros/foxy/lib/python3.8/site-packages/launch/utilities/visit_all_entities_and_collect_futures_impl.py", line 45, in visit_all_entities_and_collect_futures
futures_to_return += visit_all_entities_and_collect_futures(sub_entity, context)
File "/opt/ros/foxy/lib/python3.8/site-packages/launch/utilities/visit_all_entities_and_collect_futures_impl.py", line 38, in visit_all_entities_and_collect_futures
sub_entities = entity.visit(context)
File "/opt/ros/foxy/lib/python3.8/site-packages/launch/action.py", line 108, in visit
return self.execute(context)
File "/opt/ros/foxy/lib/python3.8/site-packages/launch/actions/include_launch_description.py", line 130, in execute
launch_description = self.__launch_description_source.get_launch_description(context)
File "/opt/ros/foxy/lib/python3.8/site-packages/launch/launch_description_source.py", line 84, in get_launch_description
self._get_launch_description(self.__expanded_location)
File "/opt/ros/foxy/lib/python3.8/site-packages/launch/launch_description_sources/any_launch_description_source.py", line 53, in _get_launch_description
return get_launch_description_from_any_launch_file(location)
File "/opt/ros/foxy/lib/python3.8/site-packages/launch/launch_description_sources/any_launch_file_utilities.py", line 56, in get_launch_description_from_any_launch_file
raise InvalidLaunchFileError(extension, likely_errors=exceptions)
launch.invalid_launch_file_error.InvalidLaunchFileError: Caught exception when trying to load file of format [py]: 'arg'