>>> str(['Itéèm 1' "Änd nümber 2 contain unicode"]).encode("ascii")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
UnicodeEncodeError: 'ascii' codec can't encode characters in position 4-5: ordinal not in range(128)

So this does not work with datatypes that are converted to unicode strings actually containing unicode characters.