UCS Upgrade to 5.0.0: Update aborted by pre-update script - dovecot and sieve related

Trying to do an upgrade from 4.4-8 errata1118 to 5.0-0, the pre-update script aborts with this error:

The following UCR templates are not compatible with Python 3:
	 /etc/univention/templates/files/var/lib/dovecot/sieve/default.sieve (package: univention-mail-dovecot)
See https://help.univention.com/t/17948 for information on how to proceed with each template.

The default.sieve seems to be standard.

Any ideas?

Please verify that you have univention-mail-dovecot version 5.0.1-13 installed:

dpkg -l univention-mail-dovecot

It ensures Python 3 compatibility of that template: Security and bugfix errata for Univention Corporate Server

If that’s the case, you must have modified the template. Please replace/update it with the current version: https://raw.githubusercontent.com/univention/univention-corporate-server/eabee553a1020d35cbdc79016c286f52d8d48886/mail/univention-mail-dovecot/conffiles/var/lib/dovecot/sieve/default.sieve

Daniel Tröder