remove_old_bin_files

# File lib/rubygems/commands/setup_command.rb, line 480
  def remove_old_bin_files(bin_dir)
    old_bin_files = {
      'gem_mirror' => 'gem mirror',
      'gem_server' => 'gem server',
      'gemlock' => 'gem lock',
      'gemri' => 'ri',
      'gemwhich' => 'gem which',
      'index_gem_repository.rb' => 'gem generate_index',
    }

    old_bin_files.each do |old_bin_file, new_name|
      old_bin_path = File.join bin_dir, old_bin_file
      next unless File.exist? old_bin_path

      deprecation_message = "`#{old_bin_file}` has been deprecated. Use `#{new_name}` instead."

      File.open old_bin_path, 'w' do |fp|
        fp.write #!#{Gem.ruby}abort "#{deprecation_message}"
      end

      next unless Gem.win_platform?

      File.open "#{old_bin_path}.bat", 'w' do |fp|
        fp.puts %{@ECHO.#{deprecation_message}}
      end
    end
  end