Will rollback the configuration to a previous state.
        Can be called also when

        :param number: How many steps back in the configuration history must look back.
        :raise pyPluribus.exceptions.RollbackError: In case the configuration cannot be rolled back.

def rollback(self, number=0):
        """
        Will rollback the configuration to a previous state.
        Can be called also when

        :param number: How many steps back in the configuration history must look back.
        :raise pyPluribus.exceptions.RollbackError: In case the configuration cannot be rolled back.
        """
        if number < 0:
            raise pyPluribus.exceptions.RollbackError("Please provide a positive number to rollback to!")
        available_configs = len(self._config_history)
        max_rollbacks = available_configs - 2
        if max_rollbacks < 0:
            raise pyPluribus.exceptions.RollbackError("Cannot rollback: \
                not enough configration history available!")
        if max_rollbacks > 0 and number > max_rollbacks:
            raise pyPluribus.exceptions.RollbackError("Cannot rollback more than {cfgs} configurations!\
                ".format(cfgs=max_rollbacks))
        config_location = 1  # will load the initial config worst case (user never commited, but wants to discard)
        if max_rollbacks > 0:  # in case of previous commit(s) will be able to load a specific configuration
            config_location = available_configs - number - 1  # stored in location len() - rollabck_nb - 1
            # covers also the case of discard uncommitted changes (rollback 0)
        desired_config = self._config_history[config_location]
        try:
            self._upload_config_content(desired_config, rollbacked=True)
        except pyPluribus.exceptions.ConfigLoadError as loaderr:
            raise pyPluribus.exceptions.RollbackError("Cannot rollback: {err}".format(err=loaderr))
        del self._config_history[(config_location+1):]  # delete all newer configurations than the config rolled back
        self._last_working_config = desired_config
        self._committed = True
        self._config_changed = False
        return True