Python have some problems with I/O being allowed only in ASCII or Unicode on some circunstances, depending on your version. It also has some problems with composing codepoints, lengths, encode translations, and other of that stuff that nobody does right.
Yet, Python has the most comprehensive support for Unicode of any language that I looked out, outside of C/C++. (Beats Perl 5 in any day. I don't know about 6.) It's just that no language has complete support (except for C/C++, that properly ignores the entire issue).