# File lib/amazon/aws.rb, line 1414
      def Error.exception(xml)
        err_class = xml.elements['Code'].text.sub( /^AWS.*\./, '' )
        err_msg = xml.elements['Message'].text

        # Dynamically define a new exception class for this class of error,
        # unless it already exists.
        #
        # Note that Ruby 1.9's Module.const_defined? needs a second parameter
        # of *false*, or it will also search AWSError's ancestors.
        #
        cd_params = [ err_class ]
        cd_params << false if RUBY_VERSION >= '1.9.0'

        unless Amazon::AWS::Error.const_defined?( *cd_params )
          Amazon::AWS::Error.const_set( err_class, Class.new( AWSError ) )
        end

        # Generate and return a new exception from the relevant class.
        #
        Amazon::AWS::Error.const_get( err_class ).new( err_msg )
      end