internal exception hook

def _excepthook(self, etype, evalue, trace):
        """
        internal exception hook
        """
        if etype == ArgumentParserError:
            self.exit(code=CRITICAL,
                      message='error: {0}'.format(evalue),
                      extdata=self.parser.format_usage())
        else:
            self.exit(code=UNKNOWN,
                      message='Uncaught exception: {0} - {1}'
                              .format(etype.__name__, evalue),
                      extdata=''.join(traceback.format_tb(trace)))