That's far from the only pitfall. For instance some of the P2 stdlib relies on implicit coercion to bytestrings whereas the Python 3 version has been properly converted to unicode (I discovered that when I tried to disable implicit coercion in one of the codebases I work with for cleanup/migration purposes).

So cross-platform string handling is not just a matter of properly splitting bytestrings and textstrings, but also finding out where "native strings" need to remain.