Upgrade code to support Django 1.10

stages/tests.py

@@ -2,8 +2,8 @@ import json
 from datetime import date
 
 from django.contrib.auth.models import User
-from django.core.urlresolvers import reverse
 from django.test import TestCase
+from django.urls import reverse
 
 from .models import (
     Level, Domain, Section, Klass, Period, Student, Corporation, Availability,