  from django.core import validators
  from django.db import models
  from django.db.models.manager import EmptyManager
  from django.utils.crypto import get_random_string
  from django.utils.http import urlquote
  from django.utils import six
  from django.utils.translation import ugettext_lazy as _
  from django.utils import timezone
  
  from django.contrib import auth
 
</s> remove from django.utils import six
 </s> add  </s> remove import datetime
from django.utils import six
 </s> add  </s> remove from django.utils._os import upath
 </s> add  </s> remove import warnings
 </s> add  </s> remove import sys
 </s> add 
  from django.core import validators
  from django.db import models
  from django.db.models.manager import EmptyManager
  from django.utils.crypto import get_random_string

  from django.utils import six
  from django.utils.translation import ugettext_lazy as _
  from django.utils import timezone
  
  from django.contrib import auth
keep keep keep keep replace keep keep keep keep keep
 Fixed a number of flake8 errors -- particularly around unused imports and local variables 
django/contrib/auth/models.py