Bug#819114: Job reported as failed, but wasn't

[Yuri D'Elia]

Package: systemd-cron
Version: 1.5.4-1
Severity: normal

I've added a cronjob that runs as my user every minute (fetchmail).
Occasionally, the job is reported as failed with the following email:

Subject: [laptop] job cron-wavexx-wavexx-0 failed

● cron-wavexx-wavexx-0.service - [Cron] "* * * * * fetchmail"
   Loaded: loaded (/var/spool/cron/crontabs/wavexx; bad; vendor preset: enabled)
   Active: inactive (dead) since Wed 2016-03-23 18:40:14 CET; 36ms ago
     Docs: man:systemd-crontab-generator(8)
  Process: 30246 ExecStart=/usr/bin/zsh -c fetchmail (code=exited, status=0/SUCCESS)
 Main PID: 30246 (code=exited, status=0/SUCCESS)

Mar 23 18:40:14 eab16011nb systemd[1]: Starting [Cron] "* * * * * fetchmail"...
Mar 23 18:40:14 eab16011nb systemd[1]: Started [Cron] "* * * * * fetchmail".

So it exited with code 0. What exactly has failed here?

-- Package-specific info:
-- output of systemd-delta

-- System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (900, 'unstable'), (800, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 4.5.0-trunk-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages systemd-cron depends on:
ii  init-system-helpers  1.29
ii  libc6                2.22-4
pn  python3:any          <none>
ii  systemd-sysv         229-3

Versions of packages systemd-cron recommends:
ii  exim4-daemon-light [mail-transport-agent]  4.86.2-2

systemd-cron suggests no packages.