Min of delay on planned departure.

def get_delay(self, planned, estimated):
        """Min of delay on planned departure."""
        delay = 0                   # default is no delay
        if estimated >= planned:    # there is a delay
            delay = round((estimated - planned).seconds / 60)
        else:                       # leaving earlier
            delay = round((planned - estimated).seconds / 60) * -1
        return delay