tools for generating worlds and wamv use extraneous levels of indirection

[M1chaelM]

This issue is related to #348 and #289. The generate_worlds aspect of our automatic evaluation tool is not currently working.

[M1chaelM]

Details

The generate_worlds.launch file loads some parameters and then calls the generate_worlds.py script as a node. generate_worlds.py runs another script by the same name (!) which does the following:

• parse .yaml files with world parameters
• create a .xacro for each world
• call rosrun xacro on the new .xacro file to create a .world file

[tfoote]

Looking into this I can confirm that there's extra levels of indirection that are not necessary.

The top level launch files: https://github.com/osrf/vrx/blob/master/vrx_gazebo/launch/generate_worlds.launch and sets several arguments which are passed in as parameters to the script.

In the main for that script they use rospy.get_param to access the values. For example:

vrx/vrx_gazebo/src/vrx_gazebo/generate_worlds.py

Line 27 in 76ae5fd

world_file = rospy.get_param('world_target') + yaml_name + \

There's no other use of the ROS runtime.

So I'd suggest changing to use argparse to do the argument parsing from the command line (instead of using roslaunch arguments) and then the script no longer will need to initialize rospy and thus doesn't need a roscore to be running. It will just need the workspace sourced. The launch files will go away and the user will just directly invoke the script using rosrun vrx_gazebo generate_worlds.py --with-cli=arguments --if-necessary

[M1chaelM]

The generate_worlds.launch error was resolved in PR #383 and it is now working properly, so the original problem this issue was meant to document is resolved. It is probably still a good idea to remove the extra indirection and the discussion above is useful for this so I'm renaming the issue to reflect this new goal.