Django RelatedObjectDoesNotExist error

I cannot see to get this to work…

I have a method has_related_object in my model that needs to check if a related object exists…

class Business(base):
      name =  models.CharField(max_length=100, blank=True, null=True)


  def has_related_object(self):
    has_customer = False
    has_car = False

    try:
        has_customer = (self.customer is not None)
    except Business.DoesNotExist:
        pass

    try:
        has_car = (self.car.park is not None)
    except Business.DoesNotExist:
        pass

    return has_customer and has_car



class Customer(base):
      name =  models.CharField(max_length=100, blank=True, null=True)
      person = models.OneToOneField('Business', related_name="customer")

Error

RelatedObjectDoesNotExist Business has no customer.

I need to check if these related objects exist but from within the business object method