presto-proxy/src/main/java/io/prestosql/proxy/ProxyResource.java/ProxyResource/handleProxyException
class ProxyResource:    private static <T> T handleProxyException(Request request, ProxyException e)
    {
        log.warn(e, "Proxy request failed: %s %s", request.getMethod(), request.getUri());
        throw badRequest(BAD_GATEWAY, e.getMessage());
    }