Init the monitored folder list.

        The list is defined in the Glances configuration file.

def __set_folder_list(self, section):
        """Init the monitored folder list.

        The list is defined in the Glances configuration file.
        """
        for l in range(1, self.__folder_list_max_size + 1):
            value = {}
            key = 'folder_' + str(l) + '_'

            # Path is mandatory
            value['indice'] = str(l)
            value['path'] = self.config.get_value(section, key + 'path')
            if value['path'] is None:
                continue
            else:
                value['path'] = nativestr(value['path'])

            # Optional conf keys
            for i in ['careful', 'warning', 'critical']:
                # Read threshold
                value[i] = self.config.get_value(section, key + i)
                if value[i] is not None:
                    logger.debug("{} threshold for folder {} is {}".format(i, value["path"], value[i]))
                # Read action
                action = self.config.get_value(section, key + i + '_action')
                if action is not None:
                    value[i + '_action'] = action
                    logger.debug("{} action for folder {} is {}".format(i, value["path"], value[i + '_action']))

            # Add the item to the list
            self.__folder_list.append(value)