py3rsa-priv2pub: 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/py3rsa-priv2pub - from package: python3-rsa

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

Error in other languages:
py3rsa-priv2pub: bevel nie gevind nie
py3rsa-priv2pub: comandă negăsită
py3rsa-priv2pub: comando não encontrado
py3rsa-priv2pub: commande introuvable
py3rsa-priv2pub: command not found
py3rsa-priv2pub: käsku ei ole
py3rsa-priv2pub: không tìm thấy lệnh
py3rsa-priv2pub: komanda nerasta
py3rsa-priv2pub: Kommando nicht gefunden.
py3rsa-priv2pub: kommandot finns inte
py3rsa-priv2pub: komut yok
py3rsa-priv2pub: nie znaleziono polecenia
py3rsa-priv2pub: níor aimsíodh an t-ordú
py3rsa-priv2pub: no se encontró la orden
py3rsa-priv2pub: no s'ha trobat l'ordre
py3rsa-priv2pub: opdracht niet gevonden
py3rsa-priv2pub: parancs nem található
py3rsa-priv2pub: perintah tidak ditemukan
py3rsa-priv2pub: príkaz nenájdený
py3rsa-priv2pub: příkaz nenalezen
py3rsa-priv2pub: команда не найдена
py3rsa-priv2pub: командата не е открита
py3rsa-priv2pub: 命令找不到
py3rsa-priv2pub: コマンドが見つかりません