Fatal error: Uncaught Error: Class "Composer\Installer\LibraryInstaller" not found in /usr/local/www/roundcube/vendor/roundcube/plugin-installer/src/ExtensionInstaller.php:16 Stack trace: #0 {main} thrown in /usr/local/www/roundcube/vendor/roundcube/plugin-installer/src/ExtensionInstaller.php on line 16