The relevant error is
---
Purging configuration files for rsyslog ...
userdel: user syslog is currently logged in
/usr/sbin/deluser: `/usr/sbin/userdel syslog' returned error code 8. Exiting.
dpkg: error processing rsyslog (--purge):
subprocess installed post-removal script returned error exit status 1
Thanks for your report.
The relevant error is
---
Purging configuration files for rsyslog ...
userdel: user syslog is currently logged in
/usr/sbin/deluser: `/usr/sbin/userdel syslog' returned error code 8. Exiting.
dpkg: error processing rsyslog (--purge):
subprocess installed post-removal script returned error exit status 1
Affecting to rsyslog