celery.py: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/lib/python3/dist-packages/celery/bin/celery.py - from package: python3-celery
/usr/lib/python2.7/dist-packages/celery/bin/celery.py - from package: python-celery

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