code: def user_exception(self, frame, exc_info):
          
          exc_type, exc_value, exc_traceback = exc_info
          frame.f_locals['__exception__'] = exc_type, exc_value
  
          # An 'Internal StopIteration' exception is an exception debug event
          # issued by the interpreter when handling a subgenerator run with
          # 'yield from' or a generator controled by a for loop. No exception has
          # actually occured in this case. The debugger uses this debug event to
          # stop when the debuggee is returning from such generators.
          prefix = 'Internal ' if (PY34 and not exc_traceback
                                      and exc_type is StopIteration) else ''
          self.message('--Exception--\n%s%s' % (prefix,
              traceback.format_exception_only(exc_type, exc_value)[-1].strip()))
          self.interaction(frame, exc_traceback)
docs: This function is called if an exception occurs,
          but only if we are to stop at or just below this level.