Check errors when loading scene geometry from files

[jonbinney]

Description

Before this PR, there was no error checking when loading planning scene geometry from a text file. This meant the caller couldn't tell whether the planning scene had been successfully loaded.

Not sure if this should be cherry-picked. It changes the return type of two PlanningScene member functions, so I think it would require people to re-compile their code.

Checklist

• Required by CI: Code is auto formatted using clang-format
• Extended the tutorials / documentation, if necessary reference
• Include a screenshot if changing a GUI
• Created tests, which fail without this PR reference
• Decide if this should be cherry-picked to other current ROS branches
• While waiting for someone to review your request, please consider reviewing another open pull request to support the maintainers

[felixvd]

I like helpful error messages, so I like this. Is there anything to update in the visualization tab?

[jonbinney]

@felixvd do you mean for the rviz plugin? I hadn't looked at that - I was actually using this function directly from a non-gui program.

[davetcoleman]

Love it

[bmagyar]

Not sure how critical this is but 1-2 unit tests would be nice. With or without, these are very welcome changes.

[jonbinney]

@bmagyar good point - I'll add a couple unit tests..

[jonbinney]

@bmagyar I've added a couple tests. Not exhaustive by any means, but should do a decent job of sanity checking the code.

[rhaschke]

I changed usages of the method in existing MoveIt! code to consider the return value.

[rhaschke]

I also approve this. Instead of returning a boolean, what about throwing an exception?
In this fashion we could also pass the error message to the caller. However, that's not the standard in ROS.

[jonbinney]

@rhaschke thanks for updating the rviz plugin to use this! Switching to exceptions seems like a bigger change - other functions in PlanningScene like processAttachedCollisionObjectMsg use a return value (bool) to indicate success/failure and I figured it would be best to keep things similar.

[jonbinney]

(if you do want exceptions here though, let me know and I'm happy to update the PR)