Add functional test to ensure response keys are not shadowed

tests/functional/test_response_shadowing.py

@@ -0,0 +1,49 @@
+# Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+# http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+from botocore.session import Session
+from nose.tools import assert_false
+
+
+def _all_services():
+    session = Session()
+    service_names = session.get_available_services()
+    for service_name in service_names:
+        yield session.get_service_model(service_name)
+
+
+def _all_operations():
+    for service_model in _all_services():
+        for operation_name in service_model.operation_names:
+            yield service_model.operation_model(operation_name)
+
+
+def _assert_not_shadowed(key, shape):
+    if not shape:
+        return
+    msg = (
+        'Found shape "%s" that shadows the botocore response key "%s"'
+    )
+    assert_false(key in shape.members, msg % (shape.name, key))
+
+
+def test_response_metadata_is_not_shadowed():
+    for operation_model in _all_operations():
+        shape = operation_model.output_shape
+        yield _assert_not_shadowed, 'ResponseMetadata', shape
+
+
+def test_exceptions_do_not_shadow():
+    for service_model in _all_services():
+        for shape in service_model.error_shapes:
+            yield _assert_not_shadowed, 'ResponseMetadata', shape
+            yield _assert_not_shadowed, 'Error', shape