I'm working on the project.task  module. I extended the model with a datetime field and extended the view so that I set the attribute required to true. Now I need a to fill this fields with a button so the user can "take" the task. 

But when the button is pressed I get the red popup "The following fields are invalid".

def take_over_task(self):
        uid = self._context.get('uid')
        now = datetime.now(pytz.timezone('Europe/Ljubljana'))

        self.sudo().task_start = datetime.strftime(now, DEFAULT_SERVER_DATETIME_FORMAT)
        self.sudo().date_deadline = datetime.strftime((now + timedelta(days=1)), DEFAULT_SERVER_DATETIME_FORMAT)
        self.sudo().user_id = uid

I know I could just execute a SQL and write this fields directly into the DB, but would like to do this a better correct way.