tidy_bytes

# File activesupport/lib/active_support/multibyte/handlers/utf8_handler.rb, line 359
      def tidy_bytes(str)
        str.split(//u).map do |c|
          if !UTF8_PAT.match(c)
            n = c.unpack('C')[0]
            n < 128 ? n.chr :
            n < 160 ? [UCD.cp1252[n] || n].pack('U') :
            n < 192 ? "\xC2" + n.chr : "\xC3" + (n-64).chr
          else
            c
          end
        end.join
      end