maas-dns fails to install due to missing config file for bind9

This may be due to an earlier partial install, but ideally the install scripts would be able to handle that case correctly.

Somehow I've gotten into a state where dpkg is trying to install bind9 before maas-dns, and it is finding maas specific config file edits in /etc/bind/named.conf, pointing to files that do not exist, because maas-dns is not (fully?) installed yet.

output from installing maas, maas-dhcp and maas-dns as dependencies of cloud-installer:

Reading package lists... Done
Building dependency tree
Reading state information... Done
0 upgraded, 0 newly installed, 0 to remove and 13 not upgraded.
6 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Setting up bind9 (1:9.9.5.dfsg-3) ...
 * Starting domain name service... bind9 [fail]
invoke-rc.d: initscript bind9, action "start" failed.
dpkg: error processing package bind9 (--configure):
 subprocess installed post-installation script returned error exit status 1
dpkg: dependency problems prevent configuration of maas-dns:
 maas-dns depends on bind9; however:
  Package bind9 is not configured yet.

dpkg: error processing package maas-dns (--configure):
 dependency problems - leaving unconfigured
Setting up maas-dhcp (1.6.0+bzr2539-0ubuntu1~beta6~ppa1) ...
No apport report written because the error message indicates its a followup error from a previous failure.
                                                                                                          maas-dhcp-server stop/pre-start, process 2438
Setting up maas-cluster-controller (1.6.0+bzr2539-0ubuntu1~beta6~ppa1) ...
 * Restarting web server apache2 AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1. Set the 'ServerName' directive globally to suppress this message
                                                                                                                                              [ OK ]
maas-pserv start/running, process 2693
maas-cluster-celery start/running, process 2728

=== at this point, it errors out.

looking at /var/log/syslog, we see this:

Jul 21 15:03:47 blackbox named[2363]: ----------------------------------------------------
Jul 21 15:03:47 blackbox named[2363]: BIND 9 is maintained by Internet Systems Consortium,
Jul 21 15:03:47 blackbox named[2363]: Inc. (ISC), a non-profit 501(c)(3) public-benefit
Jul 21 15:03:47 blackbox named[2363]: corporation. Support and training for BIND 9 are
Jul 21 15:03:47 blackbox named[2363]: available at https://www.isc.org/support
Jul 21 15:03:47 blackbox named[2363]: ----------------------------------------------------
Jul 21 15:03:47 blackbox named[2363]: adjusted limit on open files from 4096 to 1048576
Jul 21 15:03:47 blackbox named[2363]: found 4 CPUs, using 4 worker threads
Jul 21 15:03:47 blackbox named[2363]: using 4 UDP listeners per interface
Jul 21 15:03:47 blackbox named[2363]: using up to 4096 sockets
Jul 21 15:03:47 blackbox named[2363]: loading configuration from '/etc/bind/named.conf'
Jul 21 15:03:47 blackbox named[2363]: /etc/bind/named.conf.options:2: open: /etc/bind/maas/named.conf.options.inside.maas: file not found
Jul 21 15:03:47 blackbox named[2363]: loading configuration: file not found
Jul 21 15:03:47 blackbox named[2363]: exiting (due to fatal error)

=== and further investigation shows that /etc/bind/maas exists but is empty:

% ls -l /etc/bind/maas/
total 0