> I've triggered it which is why I looked for the problem and offered the defensive patch.

That's why I asked for a small example which used logging as documented and demonstrated a problem. You haven't done that.

> As API writers you can NEVER assume your parameters are what you think they should be and just blindly proceed.

I think you'll find that in Python usage in general and the Python stdlib in particular, exhaustive checking of input parameters is not the norm. I'm not saying that no error checking is ever done nor that it should never be done, but your "NEVER" doesn't seem to hold up, as the stdlib contains many counterexamples.