windmill: 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/bin/windmill - from package: python-windmill

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

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