dh_numpy3: 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/dh_numpy3 - from package: python3-numpy

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

Error in other languages:
dh_numpy3: bevel nie gevind nie
dh_numpy3: comandă negăsită
dh_numpy3: comando não encontrado
dh_numpy3: commande introuvable
dh_numpy3: command not found
dh_numpy3: käsku ei ole
dh_numpy3: không tìm thấy lệnh
dh_numpy3: komanda nerasta
dh_numpy3: Kommando nicht gefunden.
dh_numpy3: kommandot finns inte
dh_numpy3: komut yok
dh_numpy3: nie znaleziono polecenia
dh_numpy3: níor aimsíodh an t-ordú
dh_numpy3: no se encontró la orden
dh_numpy3: no s'ha trobat l'ordre
dh_numpy3: opdracht niet gevonden
dh_numpy3: parancs nem található
dh_numpy3: perintah tidak ditemukan
dh_numpy3: príkaz nenájdený
dh_numpy3: příkaz nenalezen
dh_numpy3: команда не найдена
dh_numpy3: командата не е открита
dh_numpy3: 命令找不到
dh_numpy3: コマンドが見つかりません