No Sphinx markup for PyExc_*

[encukou]

C variables for exceptions and warning categories (PyExc_*) are documented in prose, but lack Sphinx markup that would mark them as C variables. For example, searching for PyExc_BlockingIOError yields full-text results only.

This affects users of the Intersphinx inventory as well.

The names are also currently listed in the nitpick_ignore list in conf.py, since Sphinx considers them undocumented.

Linked PRs

• gh-136209: Add .. c:var:: declarations for C exception types #136210