Error about “get_currentuserinfo”

After updating Jetpack two days ago, my site keep saying this:
Notice: get_currentuserinfo is deprecated since version 4.5! Use wp_get_current_user() instead. in (name of folder) wp-includes/functions.php on line 3829

All plugins are updated and WordPress is always up to day. So, if this is the problem, the message should be displayed ages ago.

Further, I have searched the whole WordPress directory and there is no “get_currentuserinfo” in it. Weird!

Any one can offer some help?

Thanks