process_keys: 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/process_keys - from package: signing-party

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

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