Send basic message to Teams/Slack/email if sending more complex/formatted message fails

[mountaindude]

A Butler user (kudos to Henning!) recently suggested an improvement to the failed-reload alerting feature:

If sending a message to teams/slack fails, could butler perhaps send a really simple message instead that indicates that an attempt to send a message failed?

That's a great idea for several reasons:

1. The templating language used to create both email, Slack and Teams alerts is very flexible, but can also be challenging to work with. By sending a basic on-error message the Butler admin will at least get a notification that something isn't quite right.
2. The templating engine is updated every now and then and there is always a risk that such an update will break an existing butler alert template. But reverting back to sending a basic message upon failure the Butler admin will know that notifications aren't working as they should, and can take appropriate action.