Since change 7782db9260d4c6499458de4e8d9866bc0427e143 the build has been
broken. See https://gitlab.com/xen-project/xen/pipelines/20403549 for
logs. Ultimately its because HTML::TreeBuilder::XPath is now a required
Perl module. Previously the only necessary Perl modules where those
shipped in the core of Perl. While I've got no problem updating all the
containers to include it, there is a bit of a conundrum where
CentOS/RHEL don't actually package and include it. I've also checked
EPEL and its not included. Not sure what approach folks would like to
take as this will require people to bust out CPAN for RHEL/CentOS based
builds.

-- 
Doug Goldstein