pgp-clean: 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/pgp-clean - from package: signing-party

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

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