A issue is happening when trying to build apb images on branch 7.3.x.
It is something related with the apb spec label, for some reason the encoded value of apb.yaml file breakes cekit:

ERROR ('Image build failed, see logs above.', TypeError("a bytes-like object is required, not 'str'"))

Adding some debug messages, it was pointing the the spec label value with a different value than original.

To fix it a new spec value must be used, to achieve this I did a arbitrary change in one of the comments I added before.