suspicious-source: 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/suspicious-source - from package: devscripts

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

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