optparseのhelp文で改行を生かす方法

pythonのoptparseモジュールは便利だが、help文に改行を使ってもうまく表示されない。
解決の参考になるのはここの議論だろう。
以下にそのソースを抜粋。

import optparse
import textwrap

class IndentedHelpFormatterWithNL(optparse.IndentedHelpFormatter):
  def format_description(self, description):
    if not description: return ""
    desc_width = self.width - self.current_indent
    indent = " "*self.current_indent
    bits = description.split('\n')
    formatted_bits = [
      textwrap.fill(bit,
        desc_width,
        initial_indent=indent,
        subsequent_indent=indent)
      for bit in bits]
    result = "\n".join(formatted_bits) + "\n"
    return result

  def format_option(self, option):
    """
     The help for each option consists of two parts:
       * the opt strings and metavars
       eg. ("-x", or "-fFILENAME, --file=FILENAME")
       * the user-supplied help string
       eg. ("turn on expert mode", "read data from FILENAME")
    
     If possible, we write both of these on the same line:
       -x    turn on expert mode
    
     But if the opt string list is too long, we put the help
     string on a second line, indented to the same column it would
     start in if it fit on the first line.
       -fFILENAME, --file=FILENAME
           read data from FILENAME
    """
    result = []
    opts = self.option_strings[option]
    opt_width = self.help_position - self.current_indent - 2
    if len(opts) > opt_width:
      opts = "%*s%s\n" % (self.current_indent, "", opts)
      indent_first = self.help_position
    else: # start help on same line as opts
      opts = "%*s%-*s  " % (self.current_indent, "", opt_width, opts)
      indent_first = 0
    result.append(opts)
    if option.help:
      help_text = self.expand_default(option)
      help_lines = []
      for para in help_text.split("\n"):
        help_lines.extend(textwrap.wrap(para, self.help_width))
      result.append("%*s%s\n" % (
        indent_first, "", help_lines[0]))
      result.extend(["%*s%s\n" % (self.help_position, "", line)
        for line in help_lines[1:]])
    elif opts[-1] != "\n":
      result.append("\n")
    return "".join(result)

if __name__ == "__main__":
    parser = optparse.OptionParser(
      formatter=IndentedHelpFormatterWithNL(),
      usage=u"""....""")
    ....