apt-listdifferences: 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/apt-listdifferences - from package: apt-listdifferences

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

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