Failed Debian package upgrade deletes the Apache aegir.conf (symlink)

After a failed automated upgrade of aegir-provision (because I had a ~/.drush/drush_make), aegir-provision deleted by aegir.conf Apache config file, which left my server in a unusable state.

I suspect it is caused by this aegir-provision.postrm code:

    remove|upgrade|failed-upgrade|abort-install|abort-upgrade|disappear)
        # unregister apache config
        ( rm /etc/apache/conf.d/aegir.conf > /dev/null 2>&1 && invoke-rc.d apache force-reload ) || true
        ( rm /etc/apache2/conf.d/aegir.conf > /dev/null 2>&1 && invoke-rc.d apache2 force-reload ) || true

Here is the upgrade log:

Nov  1 08:54:09 rcabm cron-apt: CRON-APT RUN [/etc/cron-apt/config]: Tue Nov  1 07:56:55 EDT 2011
Nov  1 08:54:09 rcabm cron-apt: The following packages have been kept back:
Nov  1 08:54:09 rcabm cron-apt:   aegir aegir-hostmaster php5-suhosin php5-xdebug
Nov  1 08:54:09 rcabm cron-apt: The following packages will be upgraded:
Nov  1 08:54:09 rcabm cron-apt:   aegir-provision
Nov  1 08:54:09 rcabm cron-apt: Created commit 13948ae: saving uncommitted changes in /etc prior to apt run
Nov  1 08:54:09 rcabm cron-apt:  5 files changed, 2 insertions(+), 2 deletions(-)
Nov  1 08:54:09 rcabm cron-apt:  create mode 100644 apt/sources.list.d/aegir-stable.list
Nov  1 08:54:09 rcabm cron-apt: 1 upgraded, 0 newly installed, 0 to remove and 4 not upgraded.
Nov  1 08:54:09 rcabm cron-apt: Need to get 0B/104kB of archives.
Nov  1 08:54:09 rcabm cron-apt: After this operation, 45.1kB of additional disk space will be used.
Nov  1 08:54:09 rcabm cron-apt: Preparing to replace aegir-provision 1.4-1 (using .../aegir-provision_1.5-1_all.deb) ...
Nov  1 08:54:09 rcabm cron-apt: existing drush_make install in /var/aegir/.drush/drush_make detected
Nov  1 08:54:09 rcabm cron-apt: this needs to be removed or moved away for the install to be completed
Nov  1 08:54:09 rcabm cron-apt: try: rm -rf /var/aegir/.drush/drush_make
Nov  1 08:54:09 rcabm cron-apt: dpkg: error processing /var/cache/apt/archives/aegir-provision_1.5-1_all.deb (--unpack):
Nov  1 08:54:09 rcabm cron-apt:  subprocess new pre-installation script returned error exit status 1
Nov  1 08:54:09 rcabm cron-apt: Reloading web server config: apache2[Tue Nov 01 08:54:08 2011] [warn] _default_ VirtualHost overlap on port 80, the first has precedence
Nov  1 08:54:09 rcabm cron-apt: .
Nov  1 08:54:09 rcabm cron-apt: Errors were encountered while processing:
Nov  1 08:54:09 rcabm cron-apt:  /var/cache/apt/archives/aegir-provision_1.5-1_all.deb
Nov  1 08:54:09 rcabm cron-apt: Created commit dce05d6: committing changes in /etc after apt run
Nov  1 08:54:09 rcabm cron-apt:  1 files changed, 0 insertions(+), 1 deletions(-)
Nov  1 08:54:09 rcabm cron-apt:  delete mode 120000 apache2/conf.d/aegir.conf
Nov  1 08:54:09 rcabm cron-apt: E: Sub-process /usr/bin/dpkg returned an error code (1)