def get_older_backup(self, encrypted=None, compressed=None,
                         content_type=None, database=None, servername=None):
        """
        Return the older backup's file name.

        :param encrypted: Filter by encrypted or not
        :type encrypted: ``bool`` or ``None``

        :param compressed: Filter by compressed or not
        :type compressed: ``bool`` or ``None``

        :param content_type: Filter by media or database backup, must be
                             ``'db'`` or ``'media'``

        :type content_type: ``str`` or ``None``

        :param database: Filter by source database's name
        :type: ``str`` or ``None``

        :param servername: Filter by source server's name
        :type: ``str`` or ``None``

        :returns: Older file
        :rtype: ``str``

        :raises: FileNotFound: If no backup file is found
        """
        files = self.list_backups(encrypted=encrypted, compressed=compressed,
                                  content_type=content_type, database=database,
                                  servername=servername)
        if not files:
            raise FileNotFound("There's no backup file available.")
        return min(files, key=utils.filename_to_date)
Return the older backup's file name.

        :param encrypted: Filter by encrypted or not
        :type encrypted: ``bool`` or ``None``

        :param compressed: Filter by compressed or not
        :type compressed: ``bool`` or ``None``

        :param content_type: Filter by media or database backup, must be
                             ``'db'`` or ``'media'``

        :type content_type: ``str`` or ``None``

        :param database: Filter by source database's name
        :type: ``str`` or ``None``

        :param servername: Filter by source server's name
        :type: ``str`` or ``None``

        :returns: Older file
        :rtype: ``str``

        :raises: FileNotFound: If no backup file is found