in `delete': invalid byte sequence in UTF-8 (ArgumentError)

merge.rb

# encoding: utf-8

merged_file = File.open("rfc-all.txt", "w")
Dir.entries(".").each do |file|
  if (file != "rfc-all.txt" and File.extname(file) == ".txt")
    merged_file.print "#{ file }\t"
    File.open(file).each do |line|
      merged_file.print line.chomp.delete "\t"
    end
    merged_file.print "\n"
  end
end