Good news, I have error reporting working!
I created 4 categories of errors.
OBJECT: The most common, when the user tries to manipulate an object that doesn't exist. VERB: If the user directly or indirectly calls a verb and it fails. Not sure if this can even happen since I've never seen it, but since a lot of functions rely on verbs it seemed like a safe choice. SELECTION: A problem with the selection. Particularly if a function requires that a certain number of items are selected. OTHER: A default error for things like the user passing in null strings for parameters, etc.
The only thing I'm not sure about is whether to throw an error if the user calls a selection function like selection_move or selection_rotate and nothing is selected. Inkscape gives a small notification in these cases but otherwise does not complain and I have emulated this by not throwing unrecoverable errors but I would like to indicate this condition somehow.
Any ideas?
-Soren