RLException: [demo.launch] is neither a launch file in package [panda_moveit_config] nor is [panda_moveit_config] a launch file name The traceback for the exception was written to the log file

I've been following the MoveIt! tutorial for ROS Melodic on the MoveIt! [Docs page](https://ros-planning.github.io/moveit_tutorials/doc/getting_started/getting_started.html#install-ros-and-catkin "page") but couldn't launch the **demo.launch** file with: `roslaunch panda_moveit_config demo.launch rviz_tutorial:=true` I got an exception which looks like this: >RLException: [demo.launch] is neither a launch file in package [panda_moveit_config] nor is [panda_moveit_config] a launch file name The traceback for the exception was written to the log file With all the launch files including `demo.launch` in the `panda_moveit_config/launch` directory clearly visible, I'm surprise to still see an exception like this. What can I do to make use of the `demo.launch` file.