Warning: require(vendor/autoload.php): failed to open stream: No such file or directory in /usr/local/www/roundcube/vendor/masterminds/html5/example.php on line 3

Fatal error: require(): Failed opening required 'vendor/autoload.php' (include_path='.:/usr/local/share/pear') in /usr/local/www/roundcube/vendor/masterminds/html5/example.php on line 3