pyFAI-calib: 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/pyFAI-calib - from package: pyfai

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

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