dev_sign_file: 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 Debian possible default full paths are:

/usr/bin/dev_sign_file - from package: vboot-utils

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

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