Notice: Use of undefined constant JETPACK__API_BASE - assumed 'JETPACK__API_BASE' in /var/www/secret/htdocs/wp-content/plugins/slimjetpack/slimjetpack.php on line 16
I get this message after update, install is on localhost with WP_DEBUG enabled and active xdebug. If you don't dev your plugins with this as well you should really do it, else you don't notice hidden errors like this.
Not looked into the file but the double underdash
__ looks strange to me.