[florimondmanca]

Closes #1384, refs #1384 (comment).

For consideration, but I quite like this :-)

This PR changes UNSET and UnsetType so they refer to ... and builtins.ellipsis respectively, i.e. the ellipsis special value.

This is a first step that gets us the behavior we want (users can override by setting auth=..., timeout=..., and then comparing if auth is ...: ...). But there's an obvious follow-up to update our code to drop those references internally. We may want to decide to keep the UnsetType and UNSET names available in 0.17.* but mark them as deprecated — we can decide of this as a follow-up.

[florimondmanca]

… :-)

>>> import builtins
>>> builtins.ellipsis
AttributeError: module 'builtins' has no attribute 'ellipsis'

And yet mypy accepts builtins.ellipsis, since builtins.pyi defines it… Hmm, so, anyway, this won't lead us anywhere (mypy doesn't accept Ellipsis (which does exist at runtime), saying it's an "improper type" (?)), so, closing…

[lovelydinosaur]

Nice little exploration yup!
I'd been considering exactly the same.