out.log

provider.aws.region
  The region where AWS operations will take place. Examples
  are us-east-1, us-west-2, etc.

  Default: us-east-1
  Enter a value:

Refreshing Terraform state in-memory prior to plan...
The refreshed state will be used to calculate this plan, but will not be
persisted to local or remote state storage.

data.aws_db_instance.source_db: Refreshing state...
data.aws_vpc.selected: Refreshing state...
data.aws_subnet_ids.private: Refreshing state...
data.aws_security_group.db_sg: Refreshing state...
data.aws_subnet.available.0: Refreshing state...
data.aws_subnet.available.1: Refreshing state...
data.aws_subnet.available.2: Refreshing state...
Error running plan: 1 error(s) occurred:

* aws_rds_cluster.default: 1 error(s) occurred:

* aws_rds_cluster.default: Resource 'data.aws_db_instance.source_db' does not have attribute 'db_subnet_group' for variable 'data.aws_db_instance.source_db.db_subnet_group'