Rescuing ValidationError during tail following delete can lead to confusing message

[rlister]

$ stax foo delete
Really delete stack foo? y
2018-12-05 17:57:02 UTC  DELETE_IN_PROGRESS                   AWS::CloudFormation::Stack                foo       User Initiated
Stack [foo] does not exist

The does not exist is a little aggressive for an event which is the correct result of the user's intended action. It results from just printing the message for Aws::CloudFormation::Errors::ValidationError during the tail following delete.

That rescue could probably be smarter and check stack_status, printing a more "success!"-like message if DELETE_COMPLETE.