Invalid start day (valid start days are (param1))

Raise code

"wednesday",
                "thursday",
                "friday",
                "saturday",
                "sunday",
            )
            if self.start_day not in weekdays:
                raise ScheduleValueError(
                    "Invalid start day (valid start days are {})".format(weekdays)
                )
            weekday = weekdays.index(self.start_day)
            days_ahead = weekday - self.next_run.weekday()
            if days_ahead <= 0:  # Target day already happened this week
                days_ahead += 7
            self.next_run += datetime.timedelta(days_ahead) - self.period
        if self.