diff --git a/setup.py b/setup.py
index 03af344e..e6b2b376 100644
--- a/setup.py
+++ b/setup.py
@@ -4,7 +4,6 @@
 import io
 import os
 import sys
-
 from setuptools import find_packages, setup
 
 requirements_setup = ['setuptools_scm==1.15.6']
diff --git a/src/drf_yasg/codecs.py b/src/drf_yasg/codecs.py
index d52a54c7..40a9e4c8 100644
--- a/src/drf_yasg/codecs.py
+++ b/src/drf_yasg/codecs.py
@@ -1,9 +1,10 @@
+from future.utils import raise_from
+
 import copy
 import json
 from collections import OrderedDict
 
 from coreapi.compat import force_bytes
-from future.utils import raise_from
 from ruamel import yaml
 
 from . import openapi
diff --git a/src/drf_yasg/views.py b/src/drf_yasg/views.py
index b7ddffa3..b05a54a5 100644
--- a/src/drf_yasg/views.py
+++ b/src/drf_yasg/views.py
@@ -10,8 +10,7 @@
 from rest_framework.settings import api_settings
 from rest_framework.views import APIView
 
-from drf_yasg.app_settings import swagger_settings
-
+from .app_settings import swagger_settings
 from .generators import OpenAPISchemaGenerator
 from .renderers import OpenAPIRenderer, ReDocRenderer, SwaggerJSONRenderer, SwaggerUIRenderer, SwaggerYAMLRenderer
 
diff --git a/tests/test_management.py b/tests/test_management.py
index 4e0cda6e..d39e2378 100644
--- a/tests/test_management.py
+++ b/tests/test_management.py
@@ -1,3 +1,5 @@
+from six import StringIO
+
 import json
 import os
 import random
@@ -8,7 +10,6 @@
 import pytest
 from django.contrib.auth.models import User
 from django.core.management import call_command
-from six import StringIO
 
 from drf_yasg.codecs import yaml_sane_load
 
diff --git a/tox.ini b/tox.ini
index eec3bb73..195780b0 100644
--- a/tox.ini
+++ b/tox.ini
@@ -64,6 +64,11 @@ skip_glob = **/migrations/*
 atomic = true
 multi_line_output = 5
 line_length = 120
-known_standard_library = types
-known_third_party = pytest,_pytest,django,rest_framework
-known_first_party = drf_yasg
+known_future_library = future,six
+known_standard_library =
+    collections,copy,distutils,functools,inspect,io,json,logging,operator,os,pkg_resources,re,setuptools,sys,
+    types,warnings
+known_third_party =
+    coreapi,coreschema,datadiff,django,django_filters,djangorestframework_camel_case,flex,inflection,pygments,
+    pytest,rest_framework,ruamel,setuptools_scm,swagger_spec_validator,uritemplate
+known_first_party = drf_yasg,testproj,articles,snippets,users,urlconfs