Write tests for the datalake s3 bucket

[SPlanzer]

Tests are required to validate the state of the data-lake environment and src code

Discussion required:

@imincik @billgeo it would be good to discuss test strategy.

I note that the latest CDK testing docs state:

currently, TypeScript is the only supported language for testing AWS CDK infrastructure, though 
we intend to eventually make this capability available in all languages supported by the AWS CDK. 

I am therefore expecting we

• Use the PyTest framework for unit level tests that are executed locally and via CD
• Have tests that run in CD after deployment to ensure the bucket is accessible and permissions are as expected

[palmerj]

This issue might be the place to see where CDK progress is at: aws/aws-cdk-rfcs#4

[imincik]

Implemented by #23. Closing.

[l0b0]

Reopening in anticipation of A CDK assertions library for Python.