Should `None` be an acceptable `default_section` parameter of `configparser.ConfigParser`

[Avasam]

Since this is typing related, I'll ask here before adding to cpython's 5k+ issues.

In pypa/setuptools#4604 (comment) (read this comment for more details) , I found a usage of configparser.ConfigParser(default_section=None, delimiters=("=",)) seemingly to not have a default section.

The documentation doesn't make any mention of leveraging that behaviour. So we're left wondering if the parameter type should be updated (along as a request for cpython's doc to make it explicit), use "" instead, or just type-ignoring it, marking as using undocumented behaviour.

[srittau]

If it works and is in use, we should probably add this to our stubs. Looking at the CPython code, that this works looks incidental, but changing it on CPython's would break code, and would most likely need a deprecation period.

I can see adding a @deprecated marker to a None overload, though, depending on what the CPython authors say.