I faced with the issue on my own PC. For a Russian version of WinOS default PC name is ИВАН-ПК (C8 C2 C0 CD 2D CF CA in hex) and it returns from gethostbyaddr (CRT) exactly in this form (encoded with system locale cp1251 not UTF8). So when the function PyUnicode_FromString is called, it expects that argument is utf8 encoded string and throws and error.
A lot of 3rd party modules use gethostbyaddr or getfqdn (which uses gethostbyaddr) and I can't just use function that returns names as bytes. Surrogate names are also not acceptable because the name mentioned above becomes ????-??