Defined the is_registered test for views.

go/go/views.py

-from go.models import URL
+from go.models import URL, RegisteredUser
 from go.forms import URLForm
 from datetime import timedelta
 from django.http import Http404
@@ -8,6 +8,13 @@ from django.core.exceptions import PermissionDenied
 from django.contrib.auth.decorators import login_required
 from django.shortcuts import render, get_object_or_404, redirect
 
+def is_registered( user ):
+    try:
+        registered = RegisteredUser.objects.get( user=user )
+        return True
+    except RegisteredUser.DoesNotExist:
+        return False
+
 # Homepage view.
 @login_required
 def index(request):