export.pyo: 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/mailman/bin/export.pyo - from package: mailman

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

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