Validate your CloudFormation templates.
In order to pull the image, run:
docker pull almerhor/cfnlint
In order to build the image by your own, run:
docker build -t cfnlint .
In order to run the container and check the code, execute:
docker run --rm -v $(pwd)/directory:/lintfiles cfnlint \
files_to_lint
Where $(pwd)/directory is a place with CloudFormation files to lint.