if self.auto_error:
                raise self.make_not_authenticated_error()
            else:
                return None
        try:
            data = b64decode(param).decode("ascii")
        except (ValueError, UnicodeDecodeError, binascii.Error) as e:
            raise self.make_not_authenticated_error() from e
        username, separator, password = data.partition(":")

            flows=cast(OAuthFlowsModel, flows), description=description
        )
        self.scheme_name = scheme_name or self.__class__.__name__
        self.auto_error = auto_error

    def make_not_authenticated_error(self) -> HTTPException:
        """
        The OAuth 2 specification doesn't define the challenge that should be used,
        because a `Bearer` token is not really the only option to authenticate.