docs: def env(key, default=None, required=False):
      """
      Retrieves environment variables and returns Python natives. The (optional)
      default will be returned if the environment variable does not exist.
      """
      try:
          value = os.environ[key]
          return ast.literal_eval(value)
      except (SyntaxError, ValueError):
          return value
      except KeyError:
          if default or not required:
              return default
          raise ImproperlyConfigured(
              "Missing required environment variable '%s'" % key)