[1.7.x] Appeased flake8.

Backport of b1432bfc from master

django/db/migrations/state.py

@@ -89,9 +89,9 @@ class ProjectState(object):
                         # "ValueError: Lookup failed for model referenced by
                         # field migrations.Book.author: migrations.Author"
                         raise ValueError("Lookup failed for model referenced by field {field}: {model[0]}.{model[1]}{extra_message}".format(
-                            field = operations[0][1],
-                            model = lookup_model,
-                            extra_message = extra_message,
+                            field=operations[0][1],
+                            model=lookup_model,
+                            extra_message=extra_message,
                         ))
                     else:
                         do_pending_lookups(model)

tests/field_deconstruction/tests.py

@@ -3,7 +3,6 @@ import warnings
 from django.db import models
 from django.test import TestCase, override_settings
 from django.utils import six
-from django.core.files.storage import FileSystemStorage
 
 
 class FieldDeconstructionTests(TestCase):

tests/migrations/test_operations.py

@@ -757,10 +757,12 @@ class OperationTests(MigrationTestBase):
         Tests the RunPython operation correctly handles the "atomic" keyword
         """
         project_state = self.set_up_test_model("test_runpythonatomic", mti_model=True)
+
         def inner_method(models, schema_editor):
             Pony = models.get_model("test_runpythonatomic", "Pony")
             Pony.objects.create(pink=1, weight=3.55)
             raise ValueError("Adrian hates ponies.")
+
         atomic_migration = Migration("test", "test_runpythonatomic")
         atomic_migration.operations = [migrations.RunPython(inner_method)]
         non_atomic_migration = Migration("test", "test_runpythonatomic")
@@ -789,7 +791,6 @@ class OperationTests(MigrationTestBase):
             self.assertEqual(project_state.render().get_model("test_runpythonatomic", "Pony").objects.count(), 1)
 
 
-
 class MigrateNothingRouter(object):
     """
     A router that sends all writes to the other database.

tests/schema/tests.py

@@ -236,14 +236,18 @@ class SchemaTests(TransactionTestCase):
         Tests adding fields to models with a default that is not directly
         valid in the database (#22581)
         """
+
         class TestTransformField(IntegerField):
+
             # Weird field that saves the count of items in its value
             def get_default(self):
                 return self.default
+
             def get_prep_value(self, value):
                 if value is None:
                     return 0
                 return len(value)
+
         # Create the table
         with connection.schema_editor() as editor:
             editor.create_model(Author)
@@ -251,7 +255,7 @@ class SchemaTests(TransactionTestCase):
         Author.objects.create(name="Andrew", height=30)
         Author.objects.create(name="Andrea")
         # Add the field with a default it needs to cast (to string in this case)
-        new_field = TestTransformField(default={1:2})
+        new_field = TestTransformField(default={1: 2})
         new_field.set_attributes_from_name("thing")
         with connection.schema_editor() as editor:
             editor.add_field(