Bug#766345: Does not mail user in case of crontab errors

[Alexandre Detiste]

> (I'm using vixie's crontab) you cannot really assume the crontab is syntactically ok.

There is the posix standard, but there are also extra features that
are not in the standard like the "value/step"
http://pubs.opengroup.org/onlinepubs/009696699/utilities/crontab.html ;
anyway crontab(5) would be the de-facto reference on Debian.

> I noticed **none** of my user crontabs were running due to a
> systemd-crontab-generator parsing issue.
In case of error, systemd-crontab-generator should only drop the
incriminated line.

> However in these cases I would expect to receive a notification of the
> parsing/generatation error through email, exactly like cron does.
The generators runs during the early boot  and can't send e-mail
without network support and disks still mounted read-only, only log to /dev/kmsg
http://www.freedesktop.org/wiki/Software/systemd/Generators/

systemd-cron never sends e-mail by design;
but the generator could be reworked to provided an alternative
"debug/check" entry point
to ask it to validate a single crontab file/line .

This could be called during the build of the package on a test suite;
and by crontab before updating a crontab.

Alexandre Detiste