code: def _handle_nopinyin_char(chars, errors='default'):
      
      if callable_check(errors):
          return errors(chars)
  
      if errors == 'default':
          return chars
      elif errors == 'ignore':
          return None
      elif errors == 'replace':
          if len(chars) > 1:
              return ''.join(text_type('%x' % ord(x)) for x in chars)
          else:
              return text_type('%x' % ord(chars))
docs: 处理没有拼音的字符