Fix data migration

arkindex/ponos/migrations/0037_task_token.py

@@ -25,7 +25,6 @@ class Migration(migrations.Migration):
             model_name='task',
             name='token',
             field=models.CharField(
-                default=task_token_default,
                 max_length=52,
                 # Make the field temporarily nullable and not unique, so that we can
                 # fill the tokens on existing tasks before adding the constraints.