[1.7.x] Fix __latest__ to actually resolve to the latest migration

tests/migrations/test_migrations_latest_basic/0001_initial.py

@@ -0,0 +1,11 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = []
+
+    operations = []