It will be interesting to see how much logging itself needs to be aware of PEP 519 once the support is added to posixpath.  ideally, to meet the goals of PEP 519, the answer would be "not at all".

@richard: python uses duck typing: if it quacks like a duck, pretend it is a duck.  That means that the code (generally, there are exceptions) doesn't check for types, but just handles the object the way it normally would until it fails to quack, at which point you get an exception.  Sometimes we add code to turn such exceptions into clearer error messages, when the existing error *hides* what is really going on.  This would not be one of those cases though, even if supporting Path wasn't on the long term agenda: the existing error tells you that the module expects it to act like a string (support startswith, and other string methods).