python3-pyscss: 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/python3-pyscss - from package: python3-pyscss

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

Error in other languages:
python3-pyscss: bevel nie gevind nie
python3-pyscss: comandă negăsită
python3-pyscss: comando não encontrado
python3-pyscss: commande introuvable
python3-pyscss: command not found
python3-pyscss: käsku ei ole
python3-pyscss: không tìm thấy lệnh
python3-pyscss: komanda nerasta
python3-pyscss: Kommando nicht gefunden.
python3-pyscss: kommandot finns inte
python3-pyscss: komut yok
python3-pyscss: nie znaleziono polecenia
python3-pyscss: níor aimsíodh an t-ordú
python3-pyscss: no se encontró la orden
python3-pyscss: no s'ha trobat l'ordre
python3-pyscss: opdracht niet gevonden
python3-pyscss: parancs nem található
python3-pyscss: perintah tidak ditemukan
python3-pyscss: príkaz nenájdený
python3-pyscss: příkaz nenalezen
python3-pyscss: команда не найдена
python3-pyscss: командата не е открита
python3-pyscss: 命令找不到
python3-pyscss: コマンドが見つかりません