function hasCustomEndpoint(client) {
	  //if set endpoint is set for specific client, enable endpoint discovery will raise an error.
	  if (client._originalConfig && client._originalConfig.endpoint && client._originalConfig.endpointDiscoveryEnabled === true) {
	    throw util.error(new Error(), {
	      code: 'ConfigurationException',
	      message: 'Custom endpoint is supplied; endpointDiscoveryEnabled must not be true.'
	    });
	  };
	  var svcConfig = AWS.config[client.serviceIdentifier] || {};
	  return Boolean(AWS.config.endpoint || svcConfig.endpoint || (client._originalConfig && client._originalConfig.endpoint));
	}
If endpoint is explicitly configured, SDK should not do endpoint discovery in anytime.
@param [object] client Service client object.
@api private