Delete partial resource created by invalid create test

[anshikg]

*Issue #, if available:*#517

Description of changes: Adding a delete call to delete partially created resources.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[LaikaN57]

The return before finally was a bit confusing for new python devs but interesting functionality. Also I guess if the delete operation fails (due to delete code bugs) then test will provided and ERROR status instead of FAILURE which seems ok but sort of makes writing a DELETE handler a requirement of writing and testing a CREATE handler. Overall it looks good though.

[LaikaN57]

Or maybe for consistency we should be asserting as well like in the test fixture for all of the other tests? https://github.com/aws-cloudformation/cloudformation-cli/blob/master/src/rpdk/core/contract/suite/handler_create.py#L32

[ammokhov]

The return before finally was a bit confusing for new python devs but interesting functionality. Also I guess if the delete operation fails (due to delete code bugs) then test will provided and ERROR status instead of FAILURE which seems ok but sort of makes writing a DELETE handler a requirement of writing and testing a CREATE handler. Overall it looks good though.

Good point, not sure if DeleteHandler must be a requirement for the test but We should definitely try to delete created resource to avoid unexpected billing.

Or maybe for consistency we should be asserting as well like in the test fixture for all of the other tests? https://github.com/aws-cloudformation/cloudformation-cli/blob/master/src/rpdk/core/contract/suite/handler_create.py#L32

I think we could put finally as additional annotation and add that to all the necessary tests. In addition, I agree that we should be consistent and use call_and_assert