def process_handler():
			...

            # Only return request if md is valid?
            valid = True
            log.debug(f"Resource walk")
            for child in request.registry.md.rm.walk():
                log.debug(f"Resource {child.url}")
                valid = valid and child.is_valid()

            if len(request.registry.md.rm) == 0 or not valid:
                log.debug(f"Resource not valid")
				# 500: The server has either erred or is incapable of performing the requested operation.
                raise exc.exception_response(500)
            else:
                log.debug(f"Resource valid")

            return response