s390-koji: 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/s390-koji - from package: fedora-packager

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

Error in other languages:
s390-koji: bevel nie gevind nie
s390-koji: comandă negăsită
s390-koji: comando não encontrado
s390-koji: commande introuvable
s390-koji: command not found
s390-koji: käsku ei ole
s390-koji: không tìm thấy lệnh
s390-koji: komanda nerasta
s390-koji: Kommando nicht gefunden.
s390-koji: kommandot finns inte
s390-koji: komut yok
s390-koji: nie znaleziono polecenia
s390-koji: níor aimsíodh an t-ordú
s390-koji: no se encontró la orden
s390-koji: no s'ha trobat l'ordre
s390-koji: opdracht niet gevonden
s390-koji: parancs nem található
s390-koji: perintah tidak ditemukan
s390-koji: príkaz nenájdený
s390-koji: příkaz nenalezen
s390-koji: команда не найдена
s390-koji: командата не е открита
s390-koji: 命令找不到
s390-koji: コマンドが見つかりません