Here is what the error looks like:
Warning: Missing argument 3 for wpseo_upgrader_process_complete() in /home/user1/public_html/wp-content/plugins/wordpress-seo/inc/wpseo-non-ajax-functions.php on line 259
There’s nothing to worry about though, no harm is coming to your WordPress site.
Joost has a fix ready and will release it after the weekend is over, according to a tweet by Joost.
@HappyHotelier yeah we know, fix is ready, will deploy after weekend.
— Joost de Valk (@yoast) October 26, 2013