Fail to start gazebo with error "'Gazebo' is not responding".

[garrisonz]

Following the instructions of branch ros2, runing the command ros2 launch champ_config gazebo.launch.py, gazebo failed to run with the error "Gazebo is not responding".

[Rudraksh919]

This launch file tries to run outdoor.world, but the world file contains meshes that Gazebo attempts to download from an external URL (http://models.gazebosim.org). Since the URL is no longer working, Gazebo gets stuck while trying to fetch the models.