festival_client: 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/festival_client - from package: festival

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

On Debian possible default full paths are:

/usr/bin/festival_client - from package: festival

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

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