Index: sites/trunk/wordcamp.org/public_html/wp-content/mu-plugins/0-slack.php
===================================================================
--- sites/trunk/wordcamp.org/public_html/wp-content/mu-plugins/0-slack.php (revision 7855)
+++ sites/trunk/wordcamp.org/public_html/wp-content/mu-plugins/0-slack.php (revision 7960)
@@ -7,3 +7,5 @@
defined( 'WPINC' ) or die();
-require_once( __DIR__ . '/includes/slack/send.php' );
+if( is_readable( __DIR__ . '/includes/slack/send.php' ) ) {
+ require_once( __DIR__ . '/includes/slack/send.php' );
+}