Makes it clear that an error occurred. (#390)

Co-authored-by: rubenwardy <rw@rubenwardy.com>

app/templates/500.html

@@ -7,6 +7,6 @@
 {% block content %}
 	<h1>{{ self.title() }}</h1>
 	<p>
-		Don't worry, this error will have been automatically reported.
+		An error has occurred whilst loading this page. The ContentDB team has been notified.
 	</p>
 {% endblock %}