Hello! I am using ROS2 foxy with ubuntu 20.04, and I am getting this error when I try to launch a .launch.py launch file. The launch file includes launching gazebo and spawning the mobile robot described in the robot.urdf.xacro file in the launched gazebo world (let me if you need the launch file code). Below is the full terminal output of the error:

[DEBUG] [launch.launch_context]: emitting event synchronously: 'launch.events.IncludeLaunchDescription' [INFO] [launch]: All log files can be found below /home/user/.ros/log/2023-04-18-12-48-42-463391-user-Alienware-m15-R4-33093 [INFO] [launch]: Default logging verbosity is set to DEBUG [DEBUG] [launch]: processing event: '<launch.events.include_launch_description.IncludeLaunchDescription object at 0x7fe154c754f0>' [DEBUG] [launch]: processing event: '<launch.events.include_launch_description.IncludeLaunchDescription object at 0x7fe154c754f0>' ✓ '<launch.event_handlers.on_include_launch_description.OnIncludeLaunchDescription object at 0x7fe154c75130>' [DEBUG] [launch.launch_context]: emitting event: 'launch.events.Shutdown' 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=SubstitutionFailure('executed command failed. Command: xacro /home/user/ugv_ws/install/articubot_one/share/articubot_one/description/robot.urdf.xacro use_ros2_control:=true sim_mode:=true') created at /opt/ros/foxy/lib/python3.8/site-packages/launch/launch_service.py:314> source_traceback: Object created at (most recent call last):   File "/opt/ros/foxy/bin/ros2", line 11, in <module>
    load_entry_point('ros2cli==0.9.13', 'console_scripts', 'ros2')()   File "/opt/ros/foxy/lib/python3.8/site-packages/ros2cli/cli.py", line 67, in main
    rc = extension.main(parser=parser, args=args)   File "/opt/ros/foxy/lib/python3.8/site-packages/ros2launch/command/launch.py", line 151, in main
    return launch_a_launch_file(   File "/opt/ros/foxy/lib/python3.8/site-packages/ros2launch/api/api.py", line 167, in launch_a_launch_file
    ret = launch_service.run()   File "/opt/ros/foxy/lib/python3.8/site-packages/launch/launch_service.py", line 360, in run
    return loop.run_until_complete(run_async_task) File "/usr/lib/python3.8/asyncio/base_events.py", line 603, in run_until_complete
    self.run_forever()   File "/usr/lib/python3.8/asyncio/base_events.py", line 570, in run_forever
    self._run_once()   File "/usr/lib/python3.8/asyncio/base_events.py", line 1859, in _run_once
    handle._run()   File "/usr/lib/python3.8/asyncio/events.py", line 81, in _run
    self._context.run(self._callback, *self._args)   File "/opt/ros/foxy/lib/python3.8/site-packages/launch/launch_service.py", line 314, in run_async
    process_one_event_task = this_loop.create_task(self._process_one_event()) 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 45, in visit_all_entities_and_collect_futures
    futures_to_return += visit_all_entities_and_collect_futures(sub_entity, context)   [Previous line repeated 3 more times]   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_ros/actions/node.py", line 444, in execute
    self._perform_substitutions(context)   File "/opt/ros/foxy/lib/python3.8/site-packages/launch_ros/actions/node.py", line 399, in _perform_substitutions
    evaluated_parameters = evaluate_parameters(context, self.__parameters)   File "/opt/ros/foxy/lib/python3.8/site-packages/launch_ros/utilities/evaluate_parameters.py", line 164, in evaluate_parameters
    output_params.append(evaluate_parameter_dict(context, param))   File "/opt/ros/foxy/lib/python3.8/site-packages/launch_ros/utilities/evaluate_parameters.py", line 71, in evaluate_parameter_dict
    evaluated_value = perform_substitutions(context, list(value))   File "/opt/ros/foxy/lib/python3.8/site-packages/launch/utilities/perform_substitutions_impl.py", line 26, in perform_substitutions
    return ''.join([context.perform_substitution(sub) for sub in subs])   File "/opt/ros/foxy/lib/python3.8/site-packages/launch/utilities/perform_substitutions_impl.py", line 26, in <listcomp>
    return ''.join([context.perform_substitution(sub) for sub in subs])   File "/opt/ros/foxy/lib/python3.8/site-packages/launch/launch_context.py", line 232, in perform_substitution
    **return substitution.perform(self)   File "/opt/ros/foxy/lib/python3.8/site-packages/launch/substitutions/command.py", line 116, in perform
    raise SubstitutionFailure(f'executed command failed. Command: {command_str}') launch.substitutions.substitution_failure.SubstitutionFailure: executed command failed. Command: xacro /home/user/ugv_ws/install/articubot_one/share/articubot_one/description/robot.urdf.xacro use_ros2_control:=true sim_mode:=true [DEBUG] [launch]: processing event: '<launch.events.shutdown.Shutdown object at 0x7fe154c75190>' [DEBUG] [launch]: processing event: '<launch.events.shutdown.Shutdown object at 0x7fe154c75190>' ✓ '<launch.event_handlers.on_shutdown.OnShutdown object at 0x7fe154c752e0>**'


The fixes I found online for this error were restarting the terminal or rebuilding the package that contains the launch file, but both these fixes didn't work for me. Any help on how to solve this error would be greatly appreciated. Thank you!