xpt.py: 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 CentOS possible default full paths are:

/usr/lib64/xulrunner-devel-17.0.10/sdk/bin/xpt.py - from package: xulrunner-devel
/usr/lib/xulrunner-devel-17.0.10/sdk/bin/xpt.py - from package: xulrunner-devel

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/lib/icedove-devel/sdk/bin/xpt.py - from package: icedove-dev
/usr/lib/iceweasel-devel-38/sdk/bin/xpt.py - from package: iceweasel-dev

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

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