Add initial web app scaffolding

section7/templates/error.html.j2

@@ -0,0 +1,10 @@
+{% extends "base.html.j2" %}
+{% from "macros.html.j2" import make_header %}
+
+{% block header %}
+{{ make_header(title) }}
+{% endblock %}
+
+{% block content %}
+{{ error.title }}
+{% endblock %}