Incorrect line numbers in error messages #165

Migrated issue, originally created by Anonymous

The line numbers shown for runtime error messages are often
slightly too big.

As far as I could see the problem is in exceptions.py in
function _init(self, trcback), line 169. Actual code is:

      for line in module_source.split("\n"):
          match = re.match(r'\s*# SOURCE LINE (\d+)', line)
          if match:
              template_ln = int(match.group(1))
 (*)      else:
 (*)          template_ln += 1
          module_ln += 1
          line_map[module_ln] = template_ln

The two marked lines should be removed. It seems better to take
the line from the last # SOURCE LINE statement. Increasing the
line number for each python code line is not a good idea because
there is more than one python code line for one template source
line.