#[pyexception]Expand description
Helper macro to define Exception types.
More-or-less is an alias to pyclass macro.
A /// comment on the exception type is its docstring and overrides the
stored documentation. Use // for developer notes.
This macro serves a goal of generating multiple
BaseException / Exception
subtypes in a uniform and convenient manner.
It looks like SimpleExtendsException in CPython.
https://github.com/python/cpython/blob/main/Objects/exceptions.c