ndt deploy-serverless should show error message when template.yaml contains bad data

[jsyrjala]

This happens: yaml-to-yaml command fails, and deploy-serverless fails without error message

$ ndt deploy-serverless foo bar
...
+ ndt load-parameters foo -l bar -y
+ ndt yaml-to-yaml foo/serverless-bar/template.yaml
$

When I run the ndt yaml-to-yaml foo/serverless-bar/template.yaml command manually, I see the actual error.

$ ndt yaml-to-yaml foo/serverless-bar/template.yaml
ERROR: provider_iamRoleStatements_0_Resource_0_Fn::Join_1_1_: Referenced parameter "ServerlessDeploymentBucket" in file foo/serverless-bar/template.yaml not declared in template parameters in foo/serverless-bar/template.yaml
ERROR: provider_iamRoleStatements_1_Resource_0_Fn::Join_1_1_: Referenced parameter "ServerlessDeploymentBucket" in file foo/serverless-bar/template.yaml not declared in template parameters in foo/serverless-bar/template.yaml
$

deploy-serverless command should have shown me the above error message.