pybabel: 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/pybabel - from package: babel

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

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