Nope, it was me! Do throw beer-cans :-)
the MythTV sources has undergone a major rearrangement as well as change to git - and %setup had a hardcoded entry to untar a source that is not tar'ed,
looking hard at %setup fixed it.
Have rebuilt pkgutils-thunar and are testing it at the moment. Apparently the rpm command is still used - at least for unpacking src.rpm files - just fyi,