def httperror(status_code=500, message=b''):
    """Sends the given HTTP error code to the browser.

        If `flush()` has already been called, it is not possible to send
        an error, so this method will simply terminate the response.
        If output has been written but not yet flushed, it will be discarded
        and replaced with the error page.

        It is the caller's responsibility to finish the request, by calling
        finish()."""
