Comment # 3 on bug 1207520 from Stefan Dirsch

So thinks are magically working when disabling pesigning of modules, i.e. in
specfile:

-export BRP_PESIGN_FILES="*.ko"
-export BRP_PESIGN_COMPRESS_MODULE=%{compress_modules}
+export BRP_PESIGN_FILES=""
+#export BRP_PESIGN_FILES="*.ko"
+#export BRP_PESIGN_COMPRESS_MODULE=%{compress_modules}

So apparently it's pesign, which breaks the Supplements.