depmod failed on precise->trusty server upgrade

[Nick Moffitt]

A do-release-upgrade from precise to trusty on a MAAS cluster controller failed
as below. Attempting to run depmod manually causes it to exit 254. We have
not rebooted.

    Error in function:

    A fatal error occurred

    Please report this as a bug and include the files
    /var/log/dist-upgrade/main.log and /var/log/dist-upgrade/apt.log in
    your report. The upgrade has aborted.
    Your original sources.list was saved in
    /etc/apt/sources.list.distUpgrade.

    SystemError: E:Sub-process /usr/bin/dpkg returned an error code (1)

    Could not install the upgrades

    The upgrade has aborted. Your system could be in an unusable state. A
    recovery will run now (dpkg --configure -a).

    Please report this bug in a browser at
    http://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+filebug
    and attach the files in /var/log/dist-upgrade/ to the bug report.
    installArchives() failed

    Setting up linux-image-3.13.0-32-generic (3.13.0-32.57) ...
    Running depmod.
    Failed to run depmod
    dpkg: error processing package linux-image-3.13.0-32-generic (--configure):
     subprocess installed post-installation script returned error exit status 1
    dpkg: dependency problems prevent configuration of linux-image-generic:
     linux-image-generic depends on linux-image-3.13.0-32-generic; however:
      Package linux-image-3.13.0-32-generic is not configured yet.

    dpkg: error processing package linux-image-generic (--configure):
     dependency problems - leaving unconfigured
    dpkg: dependency problems prevent configuration of linux-image-server:
     linux-image-server depends on linux-image-generic (= 3.13.0.32.38); however:
      Package linux-image-generic is not configured yet.

    dpkg: error processing package linux-image-server (--configure):
     dependency problems - leaving unconfigured
    dpkg: dependency problems prevent configuration of linux-image-extra-3.13.0-32-generic:
     linux-image-extra-3.13.0-32-generic depends on linux-image-3.13.0-32-generic; however:
      Package linux-image-3.13.0-32-generic is not configured yet.

    dpkg: error processing package linux-image-extra-3.13.0-32-generic (--configure):
     dependency problems - leaving unconfigured
    Errors were encountered while processing:
     linux-image-3.13.0-32-generic
     linux-image-generic
     linux-image-server
     linux-image-extra-3.13.0-32-generic

    Upgrade complete

    The upgrade has completed but there were errors during the upgrade
    process.

    To continue please press [ENTER]