failure_message_for_should

# File lib/spec/matchers/match_array.rb, line 18
      def failure_message_for_should
        message =  "expected collection contained:  #{safe_sort(@expected).inspect}\n"
        message += "actual collection contained:    #{safe_sort(@actual).inspect}\n"
        message += "the missing elements were:      #{safe_sort(@missing_items).inspect}\n" unless @missing_items.empty?
        message += "the extra elements were:        #{safe_sort(@extra_items).inspect}\n"   unless @extra_items.empty?
        message
      end