pdb3: 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/pdb3 - from package: python3

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

Error in other languages:
pdb3: bevel nie gevind nie
pdb3: comandă negăsită
pdb3: comando não encontrado
pdb3: commande introuvable
pdb3: command not found
pdb3: käsku ei ole
pdb3: không tìm thấy lệnh
pdb3: komanda nerasta
pdb3: Kommando nicht gefunden.
pdb3: kommandot finns inte
pdb3: komut yok
pdb3: nie znaleziono polecenia
pdb3: níor aimsíodh an t-ordú
pdb3: no se encontró la orden
pdb3: no s'ha trobat l'ordre
pdb3: opdracht niet gevonden
pdb3: parancs nem található
pdb3: perintah tidak ditemukan
pdb3: príkaz nenájdený
pdb3: příkaz nenalezen
pdb3: команда не найдена
pdb3: командата не е открита
pdb3: 命令找不到
pdb3: コマンドが見つかりません