Bug#963659: pybind11: FTBFS with Sphinx 3.1: File "/usr/lib/python3/dist-packages/sphinx/domains/c.py", line 3093, in object_type / raise NotImplementedError()

[Drew Parsons]

Source: pybind11
Followup-For: Bug #963659

The new sphinx has various problems.  Let's wait for pybind11 3.2.1
and see if that fixes things.