wmllint_gui: 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/wmllint_gui - from package: wesnoth-tools

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

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