# File lib/googleauth/compute_engine.rb, line 88
      def fetch_access_token options = {}
        c = options[:connection] || Faraday.default_connection
        retry_with_error do
          headers = { "Metadata-Flavor" => "Google" }
          resp = c.get COMPUTE_AUTH_TOKEN_URI, nil, headers
          case resp.status
          when 200
            Signet::OAuth2.parse_credentials(resp.body,
                                             resp.headers["content-type"])
          when 404
            raise Signet::AuthorizationError, NO_METADATA_SERVER_ERROR
          else
            msg = "Unexpected error code #{resp.status}" \
              "#{UNEXPECTED_ERROR_SUFFIX}"
            raise Signet::AuthorizationError, msg
          end
        end
      end