making flat files delivery more robust

templates/dirnotfound.html

@@ -0,0 +1,8 @@
+{% extends "expobase.html" %}
+{% block title %}Directory not found {{ path }}{% endblock %}
+{% block body %}
+<h1>Directory not found '{{ path }}'</h1>
+<h3>Click here: <a href="/{{ subpath }}">/{{ subpath }}</a> </h3>
+<p>i.e. without the final '/' 
+{% include "menu.html" %}
+{% endblock %}