idn-lookup: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/idn-lookup - from package: heimdal-workstation

You may install the required package with command yum install {package}

Error in other languages:
idn-lookup: bevel nie gevind nie
idn-lookup: comandă negăsită
idn-lookup: comando não encontrado
idn-lookup: commande introuvable
idn-lookup: command not found
idn-lookup: käsku ei ole
idn-lookup: không tìm thấy lệnh
idn-lookup: komanda nerasta
idn-lookup: Kommando nicht gefunden.
idn-lookup: kommandot finns inte
idn-lookup: komut yok
idn-lookup: nie znaleziono polecenia
idn-lookup: níor aimsíodh an t-ordú
idn-lookup: no se encontró la orden
idn-lookup: no s'ha trobat l'ordre
idn-lookup: opdracht niet gevonden
idn-lookup: parancs nem található
idn-lookup: perintah tidak ditemukan
idn-lookup: príkaz nenájdený
idn-lookup: příkaz nenalezen
idn-lookup: команда не найдена
idn-lookup: командата не е открита
idn-lookup: 命令找不到
idn-lookup: コマンドが見つかりません