pudb3: 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/pudb3 - from package: python3-pudb

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

Error in other languages:
pudb3: bevel nie gevind nie
pudb3: comandă negăsită
pudb3: comando não encontrado
pudb3: commande introuvable
pudb3: command not found
pudb3: käsku ei ole
pudb3: không tìm thấy lệnh
pudb3: komanda nerasta
pudb3: Kommando nicht gefunden.
pudb3: kommandot finns inte
pudb3: komut yok
pudb3: nie znaleziono polecenia
pudb3: níor aimsíodh an t-ordú
pudb3: no se encontró la orden
pudb3: no s'ha trobat l'ordre
pudb3: opdracht niet gevonden
pudb3: parancs nem található
pudb3: perintah tidak ditemukan
pudb3: príkaz nenájdený
pudb3: příkaz nenalezen
pudb3: команда не найдена
pudb3: командата не е открита
pudb3: 命令找不到
pudb3: コマンドが見つかりません