Fatal error: Uncaught Error: Class "Composer\Installers\BaseInstaller" not found in /usr/local/www/wordpress/wp-content/plugins/.old/sitepress-multilingual-cms/vendor/composer/installers/src/Composer/Installers/Symfony1Installer.php:9 Stack trace: #0 {main} thrown in /usr/local/www/wordpress/wp-content/plugins/.old/sitepress-multilingual-cms/vendor/composer/installers/src/Composer/Installers/Symfony1Installer.php on line 9