'Get an object that represents this Failure\'s stack that can be passed
to traceback.extract_tb.
If the original traceback object is still present, return that. If this
traceback object has been lost but we still have the information,
return a fake traceback object (see L{_Traceback}). If there is no
traceback information at all, return None.'

def getTracebackObject(self):

    if (self.tb is not None):
        return self.tb
    elif (len(self.frames) > 0):
        return _Traceback(self.frames)
    else:
        return None
