semodule_package: 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/semodule_package - from package: policycoreutils

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

On Debian possible default full paths are:

/usr/bin/semodule_package - from package: policycoreutils

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

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