Decodes additional information about the authorization status of a request from an encoded message returned in response to an AWS request.
For example, if a user is not authorized to perform an operation that he or she has requested, the request returns a Client.UnauthorizedOperation response (an HTTP 403 response). Some AWS operations additionally return an encoded message that can provide details about this authorization failure.
原文：https://www.cnblogs.com/cloudrivers/p/11620757.html