wnpp-alert: 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/wnpp-alert - from package: devscripts

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

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