The checksum paths should be normalized by productmd starting from commit a2ff00504. The RPM in Fedora 23 does not include the patch, in rawhide it does (according to this).

So far, I don't know why the checksums are missing. Buildinstall phase creates the images and writes a treeinfo that includes them. This file should be used in write_tree_info and included in the main treeinfo. For some reason, that does not happen.

Turns out the reason why checksums are not included is that write_tree_info is not looking for the buildinstall produced file in the right place. It needs to look into subdirectory for variant. Fix is in PR #111.