Hi Colin -

In your newly found role as MC maintainer, I have a question for you: I 
am wondering about the role of errorDefinitions in MCPackageLoader. What 
errors are they supposed to capture? The only one I am aware of is when 
a variable gets moved up or down inside a package. Are there others?

(the reason I'm asking is that I fixed this case today with help from 
Eliot, so we may be able to remove this unnecessary complexity)

Cheers,
   - Andreas