gpgparticipants: 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/gpgparticipants - from package: signing-party

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

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