message: Check cert and key file
diff: @@ -697,7 +697,17 @@ static inline int socket_xport_api(php_stream *stream, Socket *sock, php_stream_
  if (!certfile || !private_key)
  {
  php_swoole_fatal_error(E_ERROR, "ssl cert/key file not found");
  - return FAILURE;
  + return PHP_STREAM_OPTION_RETURN_ERR;
  + }
  + if (access(certfile, R_OK) < 0)
  + {
  + php_swoole_fatal_error(E_ERROR, "ssl cert file[%s] not found", certfile);
  + return PHP_STREAM_OPTION_RETURN_ERR;
  + }
  + if (access(private_key, R_OK) < 0)
  + {
  + php_swoole_fatal_error(E_ERROR, "ssl key file[%s] not found", private_key);
  + return PHP_STREAM_OPTION_RETURN_ERR;
  }
  sock->ssl_option.cert_file = sw_strdup(certfile);
  