Better error messages and documentation for E2E / exec.yaml

[eyal-mor]

I took the exec/E2E yaml files from the generic example and tried to adapt to a given project. it would be nice if the error message or some docs existed about how to properly put those pieces together.

error message:

`test failure` failure:
max timed out reached for test: 'test failure' with errors: 1 error occurred:
	* max retries exceeded

`test success` failure:
missing assertion for stage DynamoDb terraform_state_locking table management

# tried also using that pipeline name instead of "Stage 1" and got similar failure.