Fix various pep8/flake8/pylint errors

tests/fake_model.py

@@ -3,7 +3,6 @@ from django.db.migrations.executor import MigrationExecutor
 from django.contrib.postgres.operations import HStoreExtension
 
 from localized_fields.models import LocalizedModel
-from localized_fields.mixins import AtomicSlugRetryMixin
 
 
 def define_fake_model(name='TestModel', fields=None):

tests/test_field.py

@@ -3,7 +3,6 @@ import json
 from django.conf import settings
 from django.db.utils import IntegrityError
 from django.test import TestCase
-from django.utils import translation
 
 from localized_fields.fields import LocalizedField
 from localized_fields.forms import LocalizedFieldForm

tests/test_model.py

@@ -34,7 +34,6 @@ class LocalizedModelTestCase(TestCase):
 
         assert isinstance(obj.title, LocalizedValue)
 
-
     @classmethod
     def test_model_init_kwargs(cls):
         """Tests whether all :see:LocalizedField

tests/test_value.py

@@ -1,5 +1,3 @@
-import json
-
 from django.conf import settings
 from django.test import TestCase
 from django.utils import translation
@@ -164,4 +162,3 @@ class LocalizedValueTestCase(TestCase):
 
         value = LocalizedValue('beer')
         assert value.get(settings.LANGUAGE_CODE) == 'beer'
-