Fixed #19462 -- Made assertQuerysetEqual detect undefined ordering

If there are more than one values to compare against and the qs isn't
ordered then assertQuerysetEqual will raise a ValueError.

tests/regressiontests/test_utils/models.py

@@ -1,5 +1,9 @@
 from django.db import models
+from django.utils.encoding import python_2_unicode_compatible
 
-
+@python_2_unicode_compatible
 class Person(models.Model):
     name = models.CharField(max_length=100)
+
+    def __str__(self):
+        return self.name