windmill_bin.py: 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/lib/python2.6/site-packages/windmill/bin/windmill_bin.py - from package: python-windmill

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

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