build/files.c in rpm-4.9.1 has
/* Arrange trailing slash on directories */
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
Yes, 4.9.1 is a broken brown-paperbag release, this has been fixed in 184.108.40.206. 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 220.127.116.11 should land there soonish).
I built rpm from git repository, which still has the broken 4.9.1.
rpm-18.104.22.168 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.