Do not warn about internal usage of ResponseTypes.CLASSES

scrapy/responsetypes.py

@@ -56,7 +56,10 @@ class ResponseTypes(metaclass=_ResponseTypesMeta):
     def __init__(self):
         self.classes = {}
         self.mimetypes = _MIME_TYPES
-        for mimetype, cls in self.CLASSES.items():
+        with catch_warnings():
+            simplefilter("ignore")
+            classes_items = self.CLASSES.items()
+        for mimetype, cls in classes_items:
             self.classes[mimetype] = load_object(cls)
 
     def __getattribute__(self, name):

tests/test_responsetypes.py

@@ -126,6 +126,10 @@ class ResponseTypesTest(unittest.TestCase):
         )
         messages = {str(warning.message) for warning in warnings}
         self.assertIn(expected_message, messages)
+        unxepected_message = (
+            'scrapy.responsetypes.ResponseTypes.CLASSES is deprecated'
+        )
+        self.assertNotIn(unxepected_message, messages)
 
     def test_class_classes_deprecation(self):
         with catch_warnings(record=True) as warnings: