Stack Create Fails: Internal Failure. Rollback requested by user.

Question

I am creating a stack via the AWS Ruby SDK v3 and it is failing with an internal error. After a long period (30-40 minutes) it fails and rolls back with an internal failure. No resources show up and there are no other events.  
  
24 May 2019 07:32:08	stack-name ROLLBACK_COMPLETE	-  
24 May 2019 07:31:42	stack-name ROLLBACK_IN_PROGRESS	Internal Failure. Rollback requested by user.  
24 May 2019 07:05:10	stack-name CREATE_IN_PROGRESS	User Initiated  
  
Launching the stack as a different (more privileged) user means that it starts immediately. I have also tried removing all resources from the stack except for one EC2 instance and the same behaviour is exhibited.   
  
The stack is launched with capabilities CAPABILITY_IAM and CAPABILITY_NAMED_IAM .  
My best guess is that the user is missing an IAM policy which allows it to even start processing the stack, but I don't know how to debug it. It's a role that is used by many other deployments and cannot be easily changed.   
Any guidance on how to debug or what might cause this behaviour is appreciated.

Answer

I worked it out.  
  
The template had a reference to a parameter being of type AWS::SSM::Parameter::Name but that was unresolvable because the account launching the CloudFormation didn't have ssm:GetParameter action permissions.   
  
A better error message and fast-failure would have been helpful in debugging this.

Stack Create Fails: Internal Failure. Rollback requested by user.

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