base_settings_v2.py

import os

from django.core.exceptions import ImproperlyConfigured

def get_env_variable(var_name):
    """ Gets the environment variable or returns exception. """
    try:
        return os.environ[var_name]
    except KeyError:
        error_msg = "Set the {} environment variable".format(var_name)
        raise ImproperlyConfigured
        
SECRET_KEY = get_env_variable('DJANGO_SECRET_KEY')