Replace django six with the python one.

Author: TheLazzziest

rest_framework_sso/utils.py

@@ -1,12 +1,14 @@
 # coding: utf-8
 from __future__ import absolute_import, unicode_literals
 
+import six
+import jwt
+
 from datetime import datetime
 
-import jwt
 from django.contrib.auth import get_user_model
 from django.core.serializers.json import DjangoJSONEncoder
-from django.utils import six, timezone
+from django.utils import timezone
 from django.utils.translation import gettext_lazy as _
 from jwt.exceptions import MissingRequiredClaimError, InvalidIssuerError, InvalidTokenError
 from rest_framework import exceptions