This bug is not currently tracked.
The error messages often aren't very good and in particular don't always tell you which file has the problem, which makes debugging rather complex.
Currently we don't always give a useful message and in particular don't always include
the file and line number of the place where the exception occured in order to give a
clue about where the error might be.
To fix this, if we get an error that isn't a ParseError, wrap it in a ParseError to give the
file and line. Also improve one error message.
There's a r+ patch which didn't land and no activity in this bug for 2 weeks.
:jgraham, could you have a look please?