def normalise(raw):
   """Normalise utf-8, double-utf-8, or iso-8859-1 to utf-8.
   Cf. http://mzz.mine.nu/m/unithing.py.txt
   and http://paste.lisp.org/display/21904,4/raw

   >>> normalise('\x97')
   '\xc2\x97'
   >>> normalise('\xe2\x80\xbd')
   '\xe2\x80\xbd'
   >>> normalise('\xc3\xa2\xc2\x80\xc2\xbd')
   '\xe2\x80\xbd'

   """
   try: uni = raw.decode('utf-8')
   except UnicodeDecodeError:
      uni = raw.decode('iso-8859-1')
      return uni.encode('utf-8')

   try:
      raw = uni.encode('iso-8859-1')
      uni.decode('utf-8')
   except UnicodeEncodeError: return raw
   return raw