Use positive_permisson.set()

RemovedInDjango20Warning: Direct assignment to the forward side of a
many-to-many set is deprecated due to the implicit save() that happens.
Use positive_permissions.set() instead.

pytest_pootle/env.py

@@ -271,13 +271,13 @@ def setup_site_permissions(self):
             'directory': Directory.objects.root}
         permission_set, created = PermissionSet.objects.get_or_create(**criteria)
         if created:
-            permission_set.positive_permissions = [view, suggest]
+            permission_set.positive_permissions.set([view, suggest])
             permission_set.save()
 
         criteria['user'] = default
         permission_set, created = PermissionSet.objects.get_or_create(**criteria)
         if created:
-            permission_set.positive_permissions = [view, suggest, translate]
+            permission_set.positive_permissions.set([view, suggest, translate])
             permission_set.save()
 
     def setup_site_root(self):