  from django.test import Client, TestCase
  from rest_framework import HTTP_HEADER_ENCODING
  from rest_framework import permissions
  from rest_framework import status
  from rest_framework.authtoken.models import Token
  from rest_framework.authentication import (
      BaseAuthentication,
      TokenAuthentication,
 
</s> remove from rest_framework.authentication import TokenAuthentication, BasicAuthentication, SessionAuthentication
 </s> add from rest_framework.authentication import (
    BaseAuthentication,
    TokenAuthentication,
    BasicAuthentication,
    SessionAuthentication
)
from rest_framework import exceptions
  from django.test import Client, TestCase
  from rest_framework import HTTP_HEADER_ENCODING
from rest_framework import exceptions
  from rest_framework import permissions
  from rest_framework import status
  from rest_framework.authtoken.models import Token
  from rest_framework.authentication import (
      BaseAuthentication,
      TokenAuthentication,
keep add keep keep keep keep keep keep
 Auth is no longer lazy.  Closes #667.

More consistent auth failure behavior. 
rest_framework/tests/authentication.py