In python 2.2, int of a unicode string containing
non-digit characters raises ValueError, like all other
attempts to convert an invalid string or unicode to
int. But in Python 2.3, it appears that int() of a
unicode string si implemented differently and now can
raise UnicodeEncodeError:

>>> int(u"\u1234")
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
UnicodeEncodeError: 'decimal' codec can't encode
character '\u1234' in position 0: invalid decimal
Unicode string
>>> 

I think it's important that int() of a string or
unicode argument only raises ValueError to indicate
invalid inputs -- otherwise one ends up writing bare
excepts for conversions to string (as it is too much
trouble to keep track of which Python versions can
raise which exceptions).