For some reason, protobuf doesn't apparently install
python/google/protobuf/proto_api.h anywhere.  For example
https://github.com/pybind/pybind11_protobuf uses it with an #include
which it assumes to find under "python" directory after fetching it
with cmake.  For packaging use that won't work and it'd help to have
it available in protobuf's packages.

I'm not quite sure whether python3-protobuf or libprotobuf-dev would
be a better choice.  Probably latter.

Hi,
 It has been left out since at least 3.14 on purpose. See the issue
this report is forwarded to.
I do not plan to force install it for the package.

Regards,
Laszlo/GCS