mass-bug: 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/mass-bug - from package: devscripts

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

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