mason-gui-text: command not found

Have You tried accessing the binary with the full path?

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 Debian possible default full paths are:

/usr/bin/mason-gui-text - from package: mason

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