Warn if remember_owner is set, but libvirt is built with --without-attr
Debian and Ubuntu have been building libvirt with --without-attr since 2014, because parts of the test suite were failing on Debian's build servers when attr was enabled. However, this is causing the remember_ownership stuff to not work as expected. On domain termination, libvirtd will simply set the uid:gid to root:root, since extended attributes are required to store and retrieve the original ownership.
It would be fantastic if this was at least logged somewhere. It would have saved me many hours of debugging, barking up the wrong tree entirely.