Finally, get it to work your bolt. However, I did it in a different way. I created folder "la_freecad" in main root of workbench and copied there all the *.py files from la_freecad and la_functions from your github.
I think it is not needed to code like this to make a Cube. You can make with single click at FreeCAD or in single line of python code. I am not sure if the "FeaturePython" coding is the right way. Maybe for extremely strange objects that cannot be done in a different way. But normally it is over-coding use
FeaturePython.
Also there is more serious problem with this type of creating objects at FreeCAD. They not match the XYZ plane axis. What makes them not manageable, a little useless.