Return a generic server error response.

def error_response(error_type="Internal server error",
                   error_text=None,
                   status=400,
                   participant=None):
    """Return a generic server error response."""
    traceback.print_exc()
    print("Error: {}.".format(error_type))

    page = error_page(
        error_text=error_text,
        error_type=error_type,
        participant=participant)

    data = {
        "status": "error",
        "html": page
    }
    return Response(dumps(data), status=status, mimetype='application/json')