Prepending to traceback

[Stefan Behnel]

Hi!

I'm writing a parser using pyparsing and I would like to augment the 
ParserException tracebacks with information about the actual error line *in 
the parsed text*. Pyparsing provides me with everything I need (parsed line 
and column), but is there a way to push that information on the traceback?


To make it a bit clearer, tracebacks currently look like this:

Traceback (most recent call last):
  ...
   File "/usr/lib/python2.4/site-packages/pyparsing.py", line 456, in parse
     loc,tokens = self.parseImpl( instring, loc, doActions )
   File "/usr/lib/python2.4/site-packages/pyparsing.py", line 727, in parseImpl
     raise exc
ParseException: Expected "SOMEOTHERTERM" (146), (5,9)


I want them to look like this:

Traceback (most recent call last):
  ...
   File "/usr/lib/python2.4/site-packages/pyparsing.py", line 456, in parse
     loc,tokens = self.parseImpl( instring, loc, doActions )
   File "/usr/lib/python2.4/site-packages/pyparsing.py", line 727, in parseImpl
     raise exc
   PyParsing, line 5, in SomeStatement
     PARSER TEST FOR TESTING MISSING TERM
ParseException: Expected "SOMEOTHERTERM" (146), (5,9)


where "PARSER TEST FOR TESTING MISSING TERM" is a line parsed by pyparsing 
that leads to raising a ParseException. I wouldn't mind too much not having 
the original traceback, though I'd prefer it. I remember having read somewhere 
that there is a way to embed an exceptions in another one, that might help.

How can I alter or create such Tracebacks?

Thanks,
Stefan