このエラーメッセージに関する原因と対処に関して説明します。
エラーメッセージ(英語)：
cloudformation template validation error
対処
関連リンク
AWS Cloudformation:Template validation error - Stack Overflow
https://stackoverflow.com/questions/47105027/aws-cloudformationtemplate-validation-error
Cloudformation, Template validation error: Invalid template ...
https://stackoverflow.com/questions/51223143/cloudformation-template-validation-error-invalid-templa・・・
AWS CloudFormation template validation error when using sed ...
https://stackoverflow.com/questions/49096152/aws-cloudformation-template-validation-error-when-using・・・
cloudformation template- validation error
https://stackoverflow.com/questions/47915035/cloudformation-template-validation-error
Cloudformation Template validation error?
https://stackoverflow.com/questions/36184101/cloudformation-template-validation-error
Cloudformation Template validation error? - Stack Overflow
https://stackoverflow.com/questions/36184101/cloudformation-template-validation-error?rq=1
Step 2. Launch the Stack - AWS Documentation
https://docs.aws.amazon.com/quickstart/latest/vpc/step2.html
Step 2. Launch the Quick Start - MongoDB on AWS
https://docs.aws.amazon.com/quickstart/latest/mongodb/step2.html
Security_Labs/cloudformation-existing-vpc.py at master - GitHub
https://github.com/HortonworksUniversity/Security_Labs/blob/master/cloudformation-existing-vpc.py
Validate CloudFormation templates - seanorama
http://seanroberts.org/cloudformation-validate/