I have recently faced this problem. When trying to update my wordpress installation to 4.3.1 by clicking on update button in admin panel.
I have forgot to remove wp-config.php before clicking Update and that is when my home page had this error.
Solution:
Step1: I have renamed or deleted setup-config.php file.
Step 2: copied my old wp-config file via FTP and
Step 3: commented the line require_once(ABSPATH . ‘wp-admin/setup-config.php’); in the old file.
-Aditya
