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

Backport of 0ed7d15563 from master

tests/admin_docs/tests.py

@@ -2,14 +2,14 @@ import sys
 import unittest
 
 from django.conf import settings
-from django.contrib.sites.models import Site
 from django.contrib.admindocs import utils
 from django.contrib.admindocs.views import get_return_data_type
 from django.contrib.auth.models import User
+from django.contrib.sites.models import Site
 from django.core.urlresolvers import reverse
 from django.test import TestCase, modify_settings, override_settings
 
-from .models import Person, Company
+from .models import Company, Person
 
 
 @override_settings(