title: Django RelatedObjectDoesNotExist error
body: <p>I cannot see to get this to work...</p>
  
  <p>I have a method <code>has_related_object</code> in my model that needs to check if a related object exists...</p>
  
  <pre><code>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")
  </code></pre>
  
  <p>Error</p>
  
  <blockquote>
    <p>RelatedObjectDoesNotExist Business has no customer.</p>
  </blockquote>
  
  <p>I need to check if these related objects exist but from within the business object method</p>