bu2sw3: 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/bu2sw3 - from package: python3-backup2swift

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

Error in other languages:
bu2sw3: bevel nie gevind nie
bu2sw3: comandă negăsită
bu2sw3: comando não encontrado
bu2sw3: commande introuvable
bu2sw3: command not found
bu2sw3: käsku ei ole
bu2sw3: không tìm thấy lệnh
bu2sw3: komanda nerasta
bu2sw3: Kommando nicht gefunden.
bu2sw3: kommandot finns inte
bu2sw3: komut yok
bu2sw3: nie znaleziono polecenia
bu2sw3: níor aimsíodh an t-ordú
bu2sw3: no se encontró la orden
bu2sw3: no s'ha trobat l'ordre
bu2sw3: opdracht niet gevonden
bu2sw3: parancs nem található
bu2sw3: perintah tidak ditemukan
bu2sw3: príkaz nenájdený
bu2sw3: příkaz nenalezen
bu2sw3: команда не найдена
bu2sw3: командата не е открита
bu2sw3: 命令找不到
bu2sw3: コマンドが見つかりません