[1.7.x] Fixed several flake8 errors

Backport of d015c9d11c from master

tests/migrations/test_operations.py

@@ -83,7 +83,7 @@ class OperationTestBase(MigrationTestBase):
                 ("pink", models.IntegerField(default=3)),
                 ("weight", models.FloatField()),
             ],
-            options = {
+            options={
                 "swappable": "TEST_SWAP_MODEL",
             },
         )]
@@ -142,7 +142,6 @@ class OperationTests(OperationTestBase):
     both forwards and backwards.
     """
 
-
     def test_create_model(self):
         """
         Tests the CreateModel operation.
@@ -1161,7 +1160,7 @@ class SwappableOperationTests(OperationTestBase):
                 ("id", models.AutoField(primary_key=True)),
                 ("pink", models.IntegerField(default=1)),
             ],
-            options = {
+            options={
                 "swappable": "TEST_SWAP_MODEL",
             },
         )

tests/schema/tests.py

@@ -7,7 +7,6 @@ from django.db import connection, DatabaseError, IntegrityError, OperationalErro
 from django.db.models.fields import IntegerField, TextField, CharField, SlugField, BooleanField, BinaryField
 from django.db.models.fields.related import ManyToManyField, ForeignKey
 from django.db.transaction import atomic
-from django.utils import six
 from .models import (Author, AuthorWithM2M, Book, BookWithLongName,
     BookWithSlug, BookWithM2M, Tag, TagIndexed, TagM2MTest, TagUniqueRename,
     UniqueTest, Thing, TagThrough, BookWithM2MThrough, AuthorTag, AuthorWithM2MThrough)