When the management commands fail, they can print something to the standard error output.
The administrator would never notice, because it wouldn't be send to him with the usual emails.
Fixes#1763
Previously the notification email sent when a box's SSL certificate
is automatically updated said, "Error Provisioning TLS Certificate"
even when there was no error. This changes the subject line to "TLS
Certificate Provisioning Results", which is more accurate.
https://discourse.mailinabox.email/t/status-check-emails-empty-after-upgrading-to-v0-16/1082/3
A user on that thread suggests an alternate solution, adding `PYTHONIOENCODING=utf-8` to `/etc/environment`. Python docs say that affects stdin/out/err. But we also use these environment variables elsewhere to ensure that config files we read/write are opened with UTF8 too. Maybe all that can be simplified too.
Refactor by moving the email-the-admin code out of the status checks and into a new separate tool.
This is why I suppressed non-error output of the backups last commit - so it doesn't send a daily email.
