AC: `NULL` defaults prevent correct signatures. Let's add `inspect.unrepresentable` to fix this

[storchaka (Serhiy Storchaka)]

See also the discussion:

Signatures, a call to action

I saw the other thread on math.log() and wanted to start a new one to shift the focus to what I think is the underlying problem than needs to be solved. If the playful story telling style doesn’t fit your tastes, please try and look past the style and focus on the substance of the post. I tried rewriting this a few times but found that the parallel construction form of comparison and contrast best communicated where work needs to be done. There once was little scripting language called Py…