multi.html: 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/share/doc/python-celery-doc/html/_modules/celery/bin/multi.html - from package: python-celery-doc

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

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