[1.7.x] Renamed tests for util -> utils moves; refs #17627.

Backport of 8a9b0c15a6 from master

tests/admin_utils/models.py

@@ -0,0 +1,64 @@
+from django.db import models
+from django.utils import six
+from django.utils.encoding import python_2_unicode_compatible
+
+
+class Article(models.Model):
+    """
+    A simple Article model for testing
+    """
+    site = models.ForeignKey('sites.Site', related_name="admin_articles")
+    title = models.CharField(max_length=100)
+    title2 = models.CharField(max_length=100, verbose_name="another name")
+    created = models.DateTimeField()
+
+    def test_from_model(self):
+        return "nothing"
+
+    def test_from_model_with_override(self):
+        return "nothing"
+    test_from_model_with_override.short_description = "not What you Expect"
+
+
+@python_2_unicode_compatible
+class Count(models.Model):
+    num = models.PositiveSmallIntegerField()
+    parent = models.ForeignKey('self', null=True)
+
+    def __str__(self):
+        return six.text_type(self.num)
+
+
+class Event(models.Model):
+    date = models.DateTimeField(auto_now_add=True)
+
+
+class Location(models.Model):
+    event = models.OneToOneField(Event, verbose_name='awesome event')
+
+
+class Guest(models.Model):
+    event = models.OneToOneField(Event)
+    name = models.CharField(max_length=255)
+
+    class Meta:
+        verbose_name = "awesome guest"
+
+
+class EventGuide(models.Model):
+    event = models.ForeignKey(Event, on_delete=models.DO_NOTHING)
+
+
+class Vehicle(models.Model):
+    pass
+
+
+class VehicleMixin(Vehicle):
+    vehicle = models.OneToOneField(Vehicle, parent_link=True, related_name='vehicle_%(app_label)s_%(class)s')
+
+    class Meta:
+        abstract = True
+
+
+class Car(VehicleMixin):
+    pass