After updating Drupal using drush my website says 'The website encountered an unexpected error. Please try again later'. with white screen(WSOD).
Then when I tried to rebuild-cache using drush there was a drush fatal error originating with rules module. I got it rectified by replacing rules module with 3.x dev version.
I could rebuild the cache and update database using drush. But still the wsod is there
My next move was to enable error reporting. So I added the line
$config['system.logging']['error_level'] = 'verbose';
it did not return any errors on the the screen.
I like to know a debugging scenario for D8 as i faced this same issue for my another D8 installation but that was rectified after rebuilding the cache. I have came across posts by user with similar issues but reasons for their issues were different. So I strongly believe that there should be a debugging scenario that can apply to all.