Scheduling .friday() jobs is only allowed for weekly jobs. Using .friday() on a job scheduled to run every 2 or more weeks is not supported.

Raise code

)
        self.start_day = "thursday"
        return self.weeks

    @property
    def friday(self):
        if self.interval != 1:
            raise IntervalError(
                "Scheduling .friday() jobs is only allowed for weekly jobs. "
                "Using .friday() on a job scheduled to run every 2 or more weeks "
                "is not supported."
            )
        self.start_day = "friday"
        return self.weeks

    @propert