AWS Toolkit prevents referencin Runtime property of AWS::Serverless::Function

[vtuhtan]

Describe the bug AWS Toolkit does not allow using reference for Runtime property of AWS::Serverless::Function. Instead parameter selection popup window, I get AWS Toolkit: Invalid runtime LambdaRuntime defined in template C:/.../PycharmProjects/<project_name>/template.yaml

To reproduce

1. Create a Parameter (e.g. LambdaRuntime, with allowed values: python3.6, python3.7 and python3.8
2. Create a function and reference LambdaRuntime parameter for Runtime property
3. Go to Deploy Serverless Application

Expected behavior SAM popup window with parameters shows up.

Screenshots

Your Environment

• OS: Windows
• JetBrains product: PyCharm Community
• JetBrains product version: 2019.3
• AWS Toolkit version: 1.12-193
• SAM CLI version: 0.47.0
• JVM/Python version: python 3.8

Additional context I am able to run

sam build 
sam deploy --guided

from CLI with referenced Runtime.

[hunterwerlla]

Currently that is not syntax we support, we require a specific runtime specified by a string. I think this would be reasonable to add support for.