Code review comment for lp:~javier.collado/utah/iso_validation_files_list

I'm getting an error for:
AssertionError: 'isolinux/adtxt.cfg' not found in:
.
./.disk
...
./isolinux/adtxt.cfg
...

The same image passes with what's currently in the dev branch.

If I have time this week, I'll see if I can find a solution, otherwise, we can revisit it when Javier returns. The docstring changes and general principle of this are good.