populate_db: Rename confusing sub local variable.

While the code was technically correct, elsewhere in that function sub
a Subscription object, not a tuple of ints.

zilencer/management/commands/populate_db.py

@@ -658,9 +658,9 @@ def fix_email(email):
                          active=pending_subs[pending_sub])
         subscriptions_to_add.append(s)
     Subscription.objects.bulk_create(subscriptions_to_add)
-    for (sub, active) in subscriptions_to_change:
-        current_subs_obj[sub].active = active
-        current_subs_obj[sub].save(update_fields=["active"])
+    for (sub_tuple, active) in subscriptions_to_change:
+        current_subs_obj[sub_tuple].active = active
+        current_subs_obj[sub_tuple].save(update_fields=["active"])
 
     subs = {}
     for sub in Subscription.objects.all():