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

Backport of 0ed7d15563 from master

tests/commands_sql_migrations/migrations/0001_initial.py

@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 from __future__ import unicode_literals
 
-from django.db import models, migrations
+from django.db import migrations, models
 
 
 class Migration(migrations.Migration):

tests/commands_sql_migrations/tests.py

@@ -3,9 +3,10 @@ from __future__ import unicode_literals
 from django.apps import apps
 from django.core.management import CommandError
 from django.core.management.color import no_style
-from django.core.management.sql import (sql_create, sql_delete, sql_indexes,
-                                        sql_destroy_indexes, sql_all)
-from django.db import connections, DEFAULT_DB_ALIAS
+from django.core.management.sql import (
+    sql_all, sql_create, sql_delete, sql_destroy_indexes, sql_indexes,
+)
+from django.db import DEFAULT_DB_ALIAS, connections
 from django.test import TestCase