Any bucket created through cloudformation will have `"LocationConstraint": null`, implying us-east-1, although in AWS CloudFormation the bucket's region will always match the template's region.
if not isinstance(prop_keys, list):
                prop_keys = [prop_keys]
            for prop_key in prop_keys:
                if prop_key == PLACEHOLDER_RESOURCE_NAME:
                    params[param_key] = resource_id
                    resource_name = get_resource_name(resource)
                    if resource_name:
                        params[param_key] = resource_name
                    else:
                        
                        try:
                            return resolve_ref(stack_name, resource_id, resources,
                                attribute='PhysicalResourceId')
                        except Exception as e:
                            LOG.debug('Unable to extract physical id for resource %s: %s' % (resource_id, e))
                else:
                    if callable(prop_key):
                        prop_value = prop_key(resource_props, stack_name=stack_name, resources=resources)
                    else:
                        prop_value = resource_props.get(prop_key)
                    if prop_value is not None:
                        params[param_key] = prop_value
    
    for param_key, prop_keys in dict(params).items():
        tmp_value = params.get(param_key)
        if tmp_value is not None:
            params[param_key] = resolve_refs_recursively(stack_name, tmp_value, resources)
        
        if str(tmp_value).lower() in ['true', 'false']:
            params[param_key] = str(tmp_value).lower() == 'true'