QFile cannot open filenames with unicode characters

Any path containing non-ascii characters can not be opened by QFile.
e.g. "/home/user/bíó.txt"

I have tried passing decoded unicode strings as well as encoded utf8 bytestrings with no effect.
I also tried using the QFile.encodeName and decodeName functions but all that did was strip the unicode characters from the filename.

This is also true for QImage (and probably others), but I assume that all goes through QFile.

I attached a script to demonstrate. If the problem occurs, its output should read:

somefile.txt was opened successfully: True
einhverskrá.txt was opened successfully: False
somefile.txt exists: True
einhverskrá.txt exists: True