# File lib/rubygems/user_interaction.rb, line 115
    def ask_yes_no(question, default=nil)
      if not @ins.tty? then
        if default.nil? then
          raise(
              Gem::OperationNotSupportedError,
              "Not connected to a tty and no default specified")
        else
          return default
        end
      end
      qstr = case default
      when nil
        'yn'
      when true
        'Yn'
      else
        'yN'
      end
      result = nil
      while result.nil?
        result = ask("#{question} [#{qstr}]")
        result = case result
        when /^[Yy].*/
          true
        when /^[Nn].*/
          false
        when /^$/
          default
        else
          nil
        end
      end
      return result
    end