selinux-policy-upgrade: 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/sbin/selinux-policy-upgrade - from package: selinux-basics

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

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