Refs #23919 -- Removed six.<various>_types usage

Thanks Tim Graham and Simon Charette for the reviews.

tests/serializers/test_xml.py

@@ -3,7 +3,6 @@ from xml.dom import minidom
 from django.core import serializers
 from django.core.serializers.xml_serializer import DTDForbidden
 from django.test import TestCase, TransactionTestCase
-from django.utils import six
 
 from .tests import SerializersTestBase, SerializersTransactionTestBase
 
@@ -34,7 +33,7 @@ class XmlSerializerTestCase(SerializersTestBase, TestCase):
     def _comparison_value(value):
         # The XML serializer handles everything as strings, so comparisons
         # need to be performed on the stringified value
-        return six.text_type(value)
+        return str(value)
 
     @staticmethod
     def _validate_output(serial_str):