==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 0.9.9
- Deployed with iRedMail Easy or the downloadable installer? download
- Linux/BSD distribution name and version: ubuntu 18.04 lts
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): mysql
- Web server (Apache or Nginx): nginx
- Manage mail accounts with iRedAdmin-Pro? no
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

on/about 12/21 the cron job for cleanup_amavisd_db.py started reporting daily after its run:

Traceback (most recent call last):
  File "/opt/www/iredadmin/tools/cleanup_amavisd_db.py", line 54, in <module>
    query_size_limit = settings.AMAVISD_CLEANUP_QUERY_SIZE_LIMIT
AttributeError: 'module' object has no attribute 'AMAVISD_CLEANUP_QUERY_SIZE_LIMIT'

not sure what to make of it. prior to the first occurrence of this error, the following apt related activities had occurred:

Start-Date: 2018-12-20  06:17:24
Commandline: /usr/bin/unattended-upgrade
Upgrade: linux-libc-dev:amd64 (4.15.0-42.45, 4.15.0-43.46)
End-Date: 2018-12-20  06:17:24

Start-Date: 2018-12-20  06:17:26
Commandline: /usr/bin/unattended-upgrade
Install: linux-headers-4.15.0-43:amd64 (4.15.0-43.46, automatic), linux-modules-4.15.0-43-generic:amd64 (4.15.0-43.46, automatic), linux-headers-4.15.0-43-generic:amd64 (4.15.0-43.46, automatic), linux-image-4.15.0-43-generic:amd64 (4.15.0-43.46, automatic)
Upgrade: linux-headers-generic:amd64 (4.15.0.42.44, 4.15.0.43.45), linux-virtual:amd64 (4.15.0.42.44, 4.15.0.43.45), linux-headers-virtual:amd64 (4.15.0.42.44, 4.15.0.43.45), linux-image-virtual:amd64 (4.15.0.42.44, 4.15.0.43.45)
End-Date: 2018-12-20  06:17:41

Start-Date: 2018-12-20  10:18:49
Commandline: apt-get dist-upgrade
Upgrade: sogo:amd64 (4.0.4.20181219-1, 4.0.4.20181220-1), sogo-activesync:amd64 (4.0.4.20181219-1, 4.0.4.20181220-1), open-iscsi:amd64 (2.0.874-5ubuntu2.4, 2.0.874-5ubuntu2.6), unattended-upgrades:amd64 (1.1ubuntu1.18.04.7, 1.1ubuntu1.18.04.8)
End-Date: 2018-12-20  10:19:12

Start-Date: 2018-12-20  10:19:36
Commandline: apt-get autoremove
Remove: linux-modules-4.15.0-39-generic:amd64 (4.15.0-39.42), linux-headers-4.15.0-39-generic:amd64 (4.15.0-39.42), linux-headers-4.15.0-39:amd64 (4.15.0-39.42), linux-image-4.15.0-39-generic:amd64 (4.15.0-39.42)
End-Date: 2018-12-20  10:19:46

any ideas? Thanks.