refinery ~ # paludis --show-reasons summary -pi world
paludis@1173467305: [WARNING] In program paludis --show-reasons summary -pi world:
  ... When performing install action from command line:
  ... When executing install task:
  ... When adding PackageDepSpec 'net-analyzer/nessus':
  ... When adding installed package 'net-analyzer/nessus-2.3.1::installed':
  ... When adding run dependencies as post dependencies:
  ... When adding PackageDepSpec '~net-analyzer/libnasl-2.3.1':
  ... When adding installed package 'net-analyzer/libnasl-2.3.1::installed':
  ... When adding run dependencies as post dependencies:
  ... When adding PackageDepSpec '=net-analyzer/nessus-libraries-2.3.1':
  ... No visible packages matching '=net-analyzer/nessus-libraries-2.3.1', falling back to installed package 'net-analyzer/nessus-libraries-2.3.1::installed'
Caught signal 2
Waiting for children...


Exiting with failure
refinery ~ # grep -i depend /usr/portage/net-analyzer/libnasl/libnasl-2.3.1.ebuild
DEPEND="~net-analyzer/nessus-libraries-${PV}"
refinery ~ # paludis -q nessus-libraries
* net-analyzer/nessus-libraries
    gentoo:            2.2.6 2.3.1-r1 {:0}
    installed:         2.3.1* {:0}
    Homepage:          http://www.nessus.org/
    Description:       A remote security scanner for Linux (nessus-libraries)
    License:           ( GPL-2 )
    Installed time:    Mon Nov 20 00:15:59 2006