semodule_unpackage: 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 Debian possible default full paths are:

/usr/bin/semodule_unpackage - from package: policycoreutils

You may install the required package with command apt-get install {package}

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