Cool, what do you think it could be?
Maybe try commenting out part of the
process() function until the error goes away, then you'll have a better idea of where to look. You can keep hitting publish in the GUI whilst you edit, plug-ins are reloaded automatically as you edit.
I suspect this one, which is trying to find a relative path from
root. Maybe the file you are editing isn't on the same drive? See if you can find a way around it.