  from django.test.utils import override_settings
  from django.utils import six
  
  from .base import IsolatedModelsTestCase
  
  
 
</s> remove         kind = models.ForeignKey(ThingKind, related_name='kinds',
                                 verbose_name=_('kind'))
 </s> add         kind = models.ForeignKey(
            ThingKind,
            on_delete=models.CASCADE,
            related_name='kinds',
            verbose_name=_('kind'),
        ) </s> remove         zip_code = models.ForeignKey(ZipCode)
 </s> add         zip_code = models.ForeignKey(
            ZipCode,
            on_delete=models.SET_NULL,
            blank=True,
            null=True,
        ) </s> remove     leader = models.ForeignKey(Actor)
 </s> add     leader = models.ForeignKey(Actor, models.CASCADE)
from django.utils.deprecation import RemovedInDjango20Warning
from django.utils.version import get_docs_version
  from django.test.utils import override_settings
  from django.utils import six
from django.utils.deprecation import RemovedInDjango20Warning
from django.utils.version import get_docs_version
  
  from .base import IsolatedModelsTestCase
  
  
keep add keep keep keep keep
 Fixed #21127 -- Started deprecation toward requiring on_delete for ForeignKey/OneToOneField 
tests/invalid_models_tests/test_relative_fields.py