Warning: require(/var/www/html/.maintenance): Failed to open stream: No such file or directory in /var/www/html/wp-includes/load.php on line 416

Fatal error: Uncaught Error: Failed opening required '/var/www/html/.maintenance' (include_path='.:/usr/local/lib/php') in /var/www/html/wp-includes/load.php:416
Stack trace:
#0 /var/www/html/wp-includes/load.php(374): wp_is_maintenance_mode()
#1 /var/www/html/wp-settings.php(77): wp_maintenance()
#2 /var/www/html/wp-config.php(175): require_once('/var/www/html/w...')
#3 /var/www/html/wp-load.php(50): require_once('/var/www/html/w...')
#4 /var/www/html/wp-blog-header.php(13): require_once('/var/www/html/w...')
#5 /var/www/html/index.php(17): require('/var/www/html/w...')
#6 {main}
  thrown in /var/www/html/wp-includes/load.php on line 416