regina-python: 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/regina-python - from package: regina-normal

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

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