FWIW, one workaround is to "monkey patch" the module:

  textwrap.TextWrapper.wordsep_re = re.compile(r'(\s+|(?<=[\w\!\"\'\&\.\,\?])-{2,}(?=\w))')

Another workaround is to "hide" the hyphens during wrapping and then restore them.
  
  def myfill(text, width=70, **kwargs):
     althyphen = chr(127)
     text = text.replace('-', althyphen)
     result = wrap(text, width, **kwargs)
     return result.replace(althyphen, '-')

That being said, I'm +1 on adding a keyword argument treating hyphens as non-breaking.