add guest role to auth

edbob/pyramid/auth.py

@@ -51,6 +51,8 @@ class EdbobAuthorizationPolicy(object):
                 user = Session.query(edbob.User).get(userid)
                 assert user
                 return has_permission(user, permission)
+        if Everyone in principals:
+            return has_permission(None, permission, session=Session())
         return False
 
     def principals_allowed_by_permission(self, context, permission):