[1.8.x] Sorted imports with isort; refs #23860.

Backport of 0ed7d15563 from master

tests/serializers/tests.py

@@ -3,10 +3,25 @@ from __future__ import unicode_literals
 
 import importlib
 import json
-from datetime import datetime
 import re
 import unittest
+from datetime import datetime
 from xml.dom import minidom
+
+from django.core import management, serializers
+from django.db import connection, transaction
+from django.test import (
+    TestCase, TransactionTestCase, override_settings, skipUnlessDBFeature,
+)
+from django.test.utils import Approximate
+from django.utils import six
+from django.utils.six import StringIO
+
+from .models import (
+    Actor, Article, Author, AuthorProfile, Category, Movie, Player, Score,
+    Team,
+)
+
 try:
     import yaml
     HAS_YAML = True
@@ -14,17 +29,6 @@ except ImportError:
     HAS_YAML = False
 
 
-from django.core import management, serializers
-from django.db import transaction, connection
-from django.test import TestCase, TransactionTestCase, override_settings, skipUnlessDBFeature
-from django.test.utils import Approximate
-from django.utils import six
-from django.utils.six import StringIO
-
-from .models import (Category, Author, Article, AuthorProfile, Actor, Movie,
-    Score, Player, Team)
-
-
 @override_settings(
     SERIALIZATION_MODULES={
         "json2": "django.core.serializers.json",