Fatal error: Uncaught Error: Interface "Composer\Plugin\PluginInterface" not found in /srv/disk1/2895578/www/whittonphotographicclub.org.uk/concrete/vendor/wikimedia/composer-merge-plugin/src/MergePlugin.php:77 Stack trace: #0 {main} thrown in /srv/disk1/2895578/www/whittonphotographicclub.org.uk/concrete/vendor/wikimedia/composer-merge-plugin/src/MergePlugin.php on line 77