The cryptography package has created all sorts of installation trouble over the last few years, probably because of mismatches between OS-installed packages and pip-installed packages. Using a virtualenv for all Python packages used by the management daemon should make sure everything is consistent.
See #1298, see #1264.
On some machines localhost is defined as something other than 127.0.0.1, and if we mix "127.0.0.1" and "localhost" then some connections won't be to to the address a service is actually running on.
This was the case with DKIM: It was running on "localhost" but Postfix was connecting to it at 127.0.0.1. (https://discourse.mailinabox.email/t/opendkim-is-not-running-port-8891/1188/12.)
I suppose "localhost" could be an alias to an IPv6 address? We don't really want local services binding on IPv6, so use "127.0.0.1" to be explicit and don't use "localhost" to be sure we get an IPv4 address.
Fixes#797
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.
