While resolving the dependency on xen-hypervisor-amd64 (a virtual
package provided by xen-hypervisor-4.0-amd64) works fine in sid[1], it
doesn't resolve for lenny-bpo[2] despite xen-hypervisor-3.2-1-amd64 from
Lenny[3] provides that[4].
[1] http://packages.debian.org/en/sid/xen-linux-system-2.6.32-5-xen-amd64
[2] http://packages.debian.org/lenny-backports/xen-linux-system-2.6.32-bpo.4-xen-amd64
[3] http://packages.debian.org/lenny/xen-hypervisor-3.2-1-amd64
[4] Provides: xen-hypervisor, xen-hypervisor-3, xen-hypervisor-3.2-1, xen-hypervisor-amd64