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

Backport of 0ed7d15563 from master

tests/test_runner/tests.py

@@ -5,17 +5,20 @@ from __future__ import unicode_literals
 
 import unittest
 
+from admin_scripts.tests import AdminScriptTestCase
+
 from django import db
 from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured
 from django.core.management import call_command
 from django.db.backends.dummy.base import DatabaseCreation
-from django.test import TestCase, TransactionTestCase, mock, skipUnlessDBFeature
+from django.test import (
+    TestCase, TransactionTestCase, mock, skipUnlessDBFeature,
+)
 from django.test.runner import DiscoverRunner, dependency_ordered
 from django.test.testcases import connections_support_transactions
 from django.utils import six
 
-from admin_scripts.tests import AdminScriptTestCase
 from .models import Person