'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 action
that he or she has requested, the request returns a
`Client.UnauthorizedOperation` response (an HTTP 403
response). Some AWS actions additionally return an encoded
message that can provide details about this authorization
failure.
Only certain AWS actions return an encoded authorization
message. The documentation for an individual action indicates
whether that action returns an encoded message in addition to
returning an HTTP code.
The message is encoded because the details of the
authorization status can constitute privileged information
that the user who requested the action should not see. To
decode an authorization status message, a user must be granted
permissions via an IAM policy to request the
`DecodeAuthorizationMessage` (
`sts:DecodeAuthorizationMessage`) action.
The decoded message includes the following type of
information:
+ Whether the request was denied due to an explicit deny or
due to the absence of an explicit allow. For more information,
see `Determining Whether a Request is Allowed or Denied`_ in
Using IAM .
+ The principal who made the request.
+ The requested action.
+ The requested resource.
+ The values of condition keys in the context of the user\'s
request.
:type encoded_message: string
:param encoded_message: The encoded message that was returned with the
response.'

def decode_authorization_message(self, encoded_message):

    params = {'EncodedMessage': encoded_message}
    return self.get_object('DecodeAuthorizationMessage', params, DecodeAuthorizationMessage, verb='POST')
