Add ability for 404 page to show error description.

realms/modules/wiki/views.py

@@ -75,7 +75,7 @@ def history(name):
         more = True
         items.pop()
     if page > 1 and not items:
-        abort(404)
+        abort(404, 'Page is past end of history.')
     for item in items:
         item['gravatar'] = gravatar_url(item['author_email'])
     return render_template('wiki/history.html', name=name, history=items,

realms/templates/errors/404.html

@@ -2,5 +2,8 @@
 {% block body %}
 
   <h1>Page Not Found</h1>
+  {% if error is defined %}
+  <h4>{{ error.description }}</h4>
+  {% endif %}
 
-{% endblock %}
+{% endblock %}