Fatal error: Uncaught Error: Call to undefined function wp_using_themes() in /var/www/topdnb/wp-includes/template-loader.php:7
Stack trace:
#0 /var/www/topdnb/wp-blog-header.php(19): require_once()
#1 /var/www/topdnb/index.php(17): require('/var/www/topdnb...')
#2 {main}
thrown in /var/www/topdnb/wp-includes/template-loader.php on line 7