pythontex: 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/pythontex - from package: texlive-extra-utils

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

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