It would be useful to have end_col and end_lineno attributes on Message objects. The way it would work is that (col, lineno) to (end_col, end_lineno) would represent the range of characters for the error. For instance, for undefined names, the col, lineno already points to the first character, and the end versions would point to the last character in the word.

I haven't looked yet how easy this is to implement. I wanted to post it here to see if anyone had any thoughts. I might make a pull request for it later (time permitting).