Handle Lua script loading errors

[fredmorcos]

Short description

Handle errors when loading Lua scripts.

Checklist

I have:

• [X] read the CONTRIBUTING.md document
• [X] compiled this code
• [ ] tested this code
• [ ] included documentation (including possible behaviour changes)
• [ ] documented the code
• [ ] added or modified regression test(s)
• [ ] added or modified unit test(s)