In [MOAB](https://bitbucket.org/fathomteam/moab/), we (optionally) depend on a rather new version of the [Metis](https://packages.debian.org/sid/metis) package, and that's what's enforced in our debian/control, too. Now, we would like to provide MOAB for older versions of Debian/Ubuntu as well, and for those older distros would drop the optional Metis dependency.