      def __check_user_settings(self, user_settings):
          SETTINGS_DOC = "http://www.django-rest-framework.org/api-guide/settings/"
          for setting in REMOVED_SETTINGS:
              if setting in user_settings:
                  raise AttributeError("The '%s' setting has been removed. Please refer to '%s' for available settings." % (setting, SETTINGS_DOC))
          return user_settings
  
  
  api_settings = APISettings(None, DEFAULTS, IMPORT_STRINGS)
  
 
</s> remove     def test_loud_error_raised_on_removed_setting(self):
 </s> add     def test_warning_raised_on_removed_setting(self): </s> remove         with self.assertRaises(AttributeError):
 </s> add         with warnings.catch_warnings(record=True) as w:
            warnings.simplefilter("always")
                warnings.warn("The '%s' setting has been removed. Please refer to '%s' for available settings." % (setting, SETTINGS_DOC), DeprecationWarning)
      def __check_user_settings(self, user_settings):
          SETTINGS_DOC = "http://www.django-rest-framework.org/api-guide/settings/"
          for setting in REMOVED_SETTINGS:
              if setting in user_settings:
                warnings.warn("The '%s' setting has been removed. Please refer to '%s' for available settings." % (setting, SETTINGS_DOC), DeprecationWarning)
          return user_settings
  
  
  api_settings = APISettings(None, DEFAULTS, IMPORT_STRINGS)
  
keep keep keep keep replace keep keep keep keep keep
 Changed error to warning message 
rest_framework/settings.py