pts-unsubscribe: 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/pts-unsubscribe - from package: devscripts

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

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