# File lib/rubygems/commands/setup_command.rb, line 351
  def remove_source_caches(install_destdir)
    if install_destdir.empty?
      require 'rubygems/source_info_cache'

      user_cache_file = File.join(install_destdir,
                                  Gem::SourceInfoCache.user_cache_file)
      system_cache_file = File.join(install_destdir,
                                    Gem::SourceInfoCache.system_cache_file)

      say "Removing old source_cache files" if Gem.configuration.really_verbose
      rm_f user_cache_file if File.writable? File.dirname(user_cache_file)
      rm_f system_cache_file if File.writable? File.dirname(system_cache_file)
    end
  end