Comment 1 for bug 1872113

Hmm, that's not ideal. The C is valid C which the compiler accepts, so I'm not sure what Sphinx is complaining about, and I don't have a system with that new a version of Sphinx.

It does suggest that we ought to make our configure --enable-werror/--disable-werror (and the code that makes the default be disable for releases) control Sphinx's warnings-as-errors option as well as the compiler's, which would at least mean that for released versions the build doesn't fail entirely on Sphinx warnings.