mutagen-pony: 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/mutagen-pony - from package: python-mutagen

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

On Debian possible default full paths are:

/usr/bin/mutagen-pony - from package: python-mutagen

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

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