Package upgrade failure: /etc/dkim.key owned by opendkim but executing uid (0) on

During packages upgrade this error occurred:

Setting up opendkim (2.11.0~alpha-10+deb9u1) …
Job for opendkim.service failed because the control process exited with error code.
See “systemctl status opendkim.service” and “journalctl -xe” for details.
invoke-rc.d: initscript opendkim, action “start” failed.
● opendkim.service - OpenDKIM DomainKeys Identified Mail (DKIM) Milter
Loaded: loaded (/lib/systemd/system/opendkim.service; enabled; vendor preset: enabled)
Active: activating (auto-restart) (Result: exit-code) since Fri 2018-07-06 17:47:50 UTC; 6ms ago
Docs: man:opendkim(8)
Process: 8365 ExecStart=/usr/sbin/opendkim -x /etc/opendkim.conf (code=exited, status=78)

Jul 06 17:47:50 … systemd[1]: opendkim.service: U…e.
Jul 06 17:47:50 … systemd[1]: opendkim.service: F…’.
Hint: Some lines were ellipsized, use -l to show in full.
dpkg: error processing package opendkim (–configure):
subprocess installed post-installation script returned error exit status 1

# journalctl -xe ... -- Unit opendkim.service has begun starting up. Jul 06 18:06:14 ... opendkim[26012]: /etc/dkim.key: key data is not secure: /etc/dkim.key is not owned by the executing uid (0) Jul 06 18:06:14 ... opendkim[26012]: opendkim: /etc/opendkim.conf: /etc/dkim.key is not owned by the executing uid (0) Jul 06 18:06:14 ... systemd[1]: opendkim.service: Control process exited, code=exited status=78 Jul 06 18:06:14 ... systemd[1]: Failed to start OpenDKIM DomainKeys Identified Mail (DKIM) Milter. -- Subject: Unit opendkim.service has failed -- Defined-By: systemd -- Support: -- -- Unit opendkim.service has failed. ... # ls -al /etc/dkim.key -rwx------ 1 opendkim opendkim 1675 Aug 6 2017 /etc/dkim.key Operating system Debian Linux 9 Webmin version 1.883 Usermin version 1.741 Virtualmin version 6.03 Theme version Authentic Theme 19.18

Apparently a new configuration file from the package needed to be accepted in place of the old file.