Provide py:: wrapper for warnings?

[virtuald]

It would be useful to be able to use that API safely available from wrapper code. It seems now that some extra effort would be needed to make it work, because sometimes it throws and sometimes it won't?

[virtuald]

I guess it wouldn't be so bad, it would probably look something like...

void ::warning(category, const char * warning, stack=1) {
    if (PyErr_WarnEx(category, warning, stack) == -1) 
        throw new pybind11::error_already_set;
}

[wjakob]

Do you want to turn this into a PR?

[virtuald]

Sure, I can make a PR this weekend. I wonder what I needed this for.

[Skylion007]

@virtuald Use deprecation warnings would be nice.

[auscompgeek]

Yeah, I think we wanted to raise DeprecationWarnings too 😄