Summary says it all, but to elaborate further: my ISO images are
stored on an LVM2 volume, while anaconda seems limited filesystems on
ordinary partitions only.
Whether or not this is worth fixing is debatable, but since you're
encouraging the use of LVM2, you might want to make anaconda support
installing from source images on LVM2 volumes.
Hard drive installs are largely deprecated. Unfortunately, adding
support for using LVM here would significantly bloat the size of the
Deferring based on Jeremy's comment.