Unescape a text string with C-style escape sequences to UTF-8 bytes.

def CUnescape(text):
  """Unescape a text string with C-style escape sequences to UTF-8 bytes."""

  def ReplaceHex(m):
    # Only replace the match if the number of leading back slashes is odd. i.e.
    # the slash itself is not escaped.
    if len(m.group(1)) & 1:
      return m.group(1) + 'x0' + m.group(2)
    return m.group(0)

  # This is required because the 'string_escape' encoding doesn't
  # allow single-digit hex escapes (like '\xf').
  result = _CUNESCAPE_HEX.sub(ReplaceHex, text)

  if str is bytes:  # PY2
    return result.decode('string_escape')
  result = ''.join(_cescape_highbit_to_str[ord(c)] for c in result)
  return (result.encode('ascii')  # Make it bytes to allow decode.
          .decode('unicode_escape')
          # Make it bytes again to return the proper type.
          .encode('raw_unicode_escape'))