docs: def to_utf8(buf, errors='replace'):
      """ Encodes a string into a UTF-8 compatible, ASCII string.
  
          `buf`
              string or unicode to convert.
  
          Returns string.
  
          * Raises a ``UnicodeEncodeError`` exception if encoding failed and
            `errors` isn't set to 'replace'.
          """
  
      if isinstance(buf, unicode):
          return buf.encode('utf-8', errors)
  
      else:
          return buf