I discussed the "rpath question" with different people. At the end, I think that the Fedora patch is "temporary fix" which we kept for way too long :-) We should remove this patch and ensure that upstream C extensions respect our rpath policy (Debian, OpenSuse, Fedora are against the usage of rpath).

I discussed with Miro Hrončok who is part of FESco (Fedora Engineering Steering Committee) and he created an issue to propose to make the build of a package *fail* if it uses rpath:
https://pagure.io/packaging-committee/issue/886

That change would be affect the whole Fedora project, not just python packages. IMHO it's a better approach than trying to exclude rpath for LIBDIR which is equal to /usr/lib64.

For these reasons, I close the issue and we will change Fedora instead.

Thanks everybody who was involved in this discussion, I learnt a lot! :-)