hy3: 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/hy3 - from package: python3-hy

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

Error in other languages:
hy3: bevel nie gevind nie
hy3: comandă negăsită
hy3: comando não encontrado
hy3: commande introuvable
hy3: command not found
hy3: käsku ei ole
hy3: không tìm thấy lệnh
hy3: komanda nerasta
hy3: Kommando nicht gefunden.
hy3: kommandot finns inte
hy3: komut yok
hy3: nie znaleziono polecenia
hy3: níor aimsíodh an t-ordú
hy3: no se encontró la orden
hy3: no s'ha trobat l'ordre
hy3: opdracht niet gevonden
hy3: parancs nem található
hy3: perintah tidak ditemukan
hy3: príkaz nenájdený
hy3: příkaz nenalezen
hy3: команда не найдена
hy3: командата не е открита
hy3: 命令找不到
hy3: コマンドが見つかりません