Better error description for "Failed to set up mount namespacing: No such file or directory"

[kokizzu]

Is your feature request related to a problem? Please describe.
Always frustrated when writing service file but it didn't show which file/directory that does not exists.

example:

InaccessiblePaths=/some/typo /bunch/other/directory
ReadWriteDirectories=/some/non/existent/directory /bunch/other/directory
ReadOnlyPaths=/some/other/typo /bunch/other/paths
ProtectHome=true
ProtectSystem=full

Describe the solution you'd like
Show which rule that causes the error (at least the path/directory), instead of just Failed to set up mount namespacing: No such file or directory

Describe alternatives you've considered
I've tried to set Environment=SYSTEMD_LOG_LEVEL=debug on service file or LogLevel=info on /etc/systemd/system.conf but it doesn't help much, the same unhelpful error "no such file or directory" without mentioning which directory/path that causes the error

[yuwata]

Please try systemd-analyze log-level debug.

[poettering]

This has been reworked in 7cc5ef5 already (which is going to be part of the next release). Let's consider this closed, hence.