weblate-integration: errors are not shown in systemd logs

Ref: #1 (closed)

Logging should be reviewed because weblate-integration was recently migrated to systemd and the journal is not showing errors correcly.

To reproduce: write something (to stdout or stderr) in /var/lib/weblate/scripts/weblate-integration.sh, trigger the job, see that it doesn't land in the journal.