Bug#923299: /lib/systemd/system/tomcat9.service: tomcat9 fails to run; "Failed to set up mount namespacing" in system log

[Felicia]

Package: tomcat9
Version: 9.0.16-2
Severity: important
File: /lib/systemd/system/tomcat9.service

Dear Maintainer,

A fresh install of tomcat9 results in the daemon failing to run with a cryptic error in syslog:

   tomcat9.service: Failed to set up mount namespacing: No such file or directory

The problem is caused from this line in the tomcat9 systemd unit file /lib/systemd/system/tomcat9.service:
    ReadWritePaths=/var/lib/solr/

Commenting out that line and doing:
   systemctl daemon-reload
   systemctl restart tomcat9.service

enables tomcat9 to run.

Perhaps tomcat9 is expecting the solr-tomcat package to be installed (which it is not on my system)?

This bug at systemd github is related:
    Misleading error message when ReadWritePaths doesn't exist #10972
    https://github.com/systemd/systemd/issues/10972




-- System Information:
Debian Release: buster/sid
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.19.16 (SMP w/4 CPU cores)
Kernel taint flags: TAINT_OOT_MODULE
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE= (charmap=UTF-8)
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages tomcat9 depends on:
ii  lsb-base        10.2018112800
ii  systemd         241-1
ii  tomcat9-common  9.0.16-2
ii  ucf             3.0038+nmu1

Versions of packages tomcat9 recommends:
ii  libtcnative-1  1.2.21-1

Versions of packages tomcat9 suggests:
ii  tomcat9-admin     9.0.16-2
pn  tomcat9-docs      <none>
ii  tomcat9-examples  9.0.16-2
pn  tomcat9-user      <none>

-- Configuration Files:
/etc/tomcat9/policy.d/01system.policy [Errno 13] Permission denied: '/etc/tomcat9/policy.d/01system.policy'
/etc/tomcat9/policy.d/02debian.policy [Errno 13] Permission denied: '/etc/tomcat9/policy.d/02debian.policy'
/etc/tomcat9/policy.d/03catalina.policy [Errno 13] Permission denied: '/etc/tomcat9/policy.d/03catalina.policy'
/etc/tomcat9/policy.d/04webapps.policy [Errno 13] Permission denied: '/etc/tomcat9/policy.d/04webapps.policy'
/etc/tomcat9/policy.d/50local.policy [Errno 13] Permission denied: '/etc/tomcat9/policy.d/50local.policy'

-- no debconf information