Test boot_partition with a valid numeric partition that does not exist on the device.

-- File fs/open~_tmp_sysinfo_board_name.txt --
linksys,e7350
-- End --

-- File fs/popen~fw_printenv_-n_bootimage_2_dev_null.txt --
1
-- End --

-- Testcase --
let ar = require('advanced_reboot');
let api = ar["luci.advanced-reboot"];
let result = api.boot_partition.call({ args: { number: "9" } });
printf("%J\n", result);
-- End --

-- Expect stdout --
{ "error": "PARTITION_NOT_FOUND", "args": [ "9" ] }
-- End --