Thank you very much for reporting this issue. I confirm this happens
when purging the package only. The offending chown was first introduced
in the tomcat6 package 6 years ago  as part of the fix for #567548.
The same issue is also found in the tomcat7 package.
Do you think running something like "chmod -R 640 /etc/tomcat8" right
before the chown is an appropriate solution to this issue?
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debian-j...@lists.debian.org for discussions and questions.