*cfn-lint version: 0.35.0

After validating a template that had a Sub function use like this:

field: !Sub
- "my string with ${parameter}
- parameter: 10

I received the following error message:
E1019 Sub parameter should be an object of 1 or string for *trimmed path*Fn::Sub
This message did not help me understand that the object cannot have an integer value, but only a string.

Check to confirm CloudTrail is configured for multi-region.

CloudFormation - IsMultiRegionTrail: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-cloudtrail-trail.html

While testing another PR, I found that mu pipeline logs command displays information from the pipelines, but also shows this error:

$ mu pipeline logs
[... normal, expected output ...]
func1 ▶ ERROR  ResourceNotFoundException: The specified log group does not exist.
	status code: 400, request id: f7260741-7f69-4772-b4cc-7c6a9c22d264

This error does not occur with the `-f

Seems like we can encrypt environment variables effectively for free by adding a KmsKeyArn property to functions. See: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md

This would be an easy contribution for a first timer...

The current behavior of --interactive is that any new stacks will get created, without any prompt. But this can be potentially dangerous (or at the very least, annoying) if you accidentally make a change, like changing the stack name, resulting in a whole new stack getting created.

Should stacker prompt you before creating a stack when using --interactive mode?

Add error handling during credentials onChange event so that the Scan Account feature does not activate if credentials are invalid