build/files.c in rpm-4.9.1 has /* Arrange trailing slash on directories */ if (fl->isDir) diskPath = rstrcat(&diskPath, "/"); which leads to a trailing slash on directories in file list in a rpm. It is incompatible with rpms built with older rpm, which require directories without trailing slash on directories.
Yes, 4.9.1 is a broken brown-paperbag release, this has been fixed in 4.9.1.1. Note that 4.9.1 was never pushed as an update for F15 so it's not affected, unless you manually build rpm from dist-git which does currently have 4.9.1 (it was intended to go as an update to f15 but will obviously be skipped and 4.9.1.1 should land there soonish).
I built rpm from git repository, which still has the broken 4.9.1.
rpm-4.9.1.1 is in dist-git now, closing this as F15 was only affected at the git repository level. And actual update is also being built right now but that's another story.