source-directory interfaces.d causes crash

# virsh iface-list
error: Failed to list interfaces
error: internal error: failed to get number of host interfaces: unspecified error - errors in loading some config files

root@noc1:/etc/libvirt/hooks# more /etc/network/interfaces
source-directory interfaces.d

# cat /etc/network/interfaces
source-directory /etc/network/interfaces.d

Also fails if:

# cat /etc/network/interfaces
source-directory interfaces.d

Change the file as follows, all good.
# cat interfaces
auto lo
iface lo inet loopback

root@noc1:/etc/network# virsh iface-list
 Name State MAC Address
---------------------------------------------------
 lo active 00:00:00:00:00:00

However the source-directory facility is important to maintaining advanced networks.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: libnetcf1 1:0.2.3-4ubuntu1
ProcVersionSignature: Ubuntu 3.13.0-73.116-generic 3.13.11-ckt30
Uname: Linux 3.13.0-73-generic x86_64
NonfreeKernelModules: zfs zunicode zcommon znvpair zavl
ApportVersion: 2.14.1-0ubuntu3.19
Architecture: amd64
Date: Thu Dec 17 12:45:52 2015
InstallationDate: Installed on 2014-03-20 (636 days ago)
InstallationMedia: Xubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: netcf
UpgradeStatus: Upgraded to trusty on 2014-04-24 (602 days ago)