  import re
  import time
  
  from django.conf import settings
  from django.core.cache import caches
  from django.http import HttpResponse, HttpResponseNotModified
 
</s> remove from django.utils.deprecation import MiddlewareMixin
 </s> add from django.utils.deprecation import MiddlewareMixin, RemovedInDjango21Warning </s> remove from django.utils.cache import get_conditional_response
 </s> add from django.utils.cache import (
    cc_delim_re, get_conditional_response, set_response_etag,
) </s> remove or you can rely on the :class:`~django.middleware.common.CommonMiddleware`
 </s> add or you can rely on the :class:`~django.middleware.http.ConditionalGetMiddleware`
import warnings
  import re
  import time
import warnings
  
  from django.conf import settings
  from django.core.cache import caches
  from django.http import HttpResponse, HttpResponseNotModified
keep add keep keep keep keep
 Fixed #26447 -- Deprecated settings.USE_ETAGS in favor of ConditionalGetMiddleware. 
django/utils/cache.py