I am using the **latest** localstack docker image to test aws s3, lambda and cloudformation locally. s3 and lambda seems to be working fine but when I call cloudformation **create-stack** api it gives me a 502 BadGateway error. This is the command I am using

`aws cloudformation create-stack \
  --template-body template.yaml \
  --stack-name cfn-test \
  --parameters ParameterKey=BucketPrefix,ParameterValue=demo-bucket \
  --endpoint-url=http://localhost:4581`

This is the error I get:
`An error occurred (502) when calling the CreateStack operation (reached max retries: 4): Bad Gateway`

From docker logs I got the following error
`2019-12-31T22:12:09:ERROR:localstack.services.generic_proxy: Error forwarding request: 'str' object has no attribute 'get' Traceback (most recent call last):
  File "/opt/code/localstack/localstack/services/generic_proxy.py", line 242, in forward
    path=path, data=data, headers=forward_headers)
  File "/opt/code/localstack/localstack/services/cloudformation/cloudformation_listener.py", line 164, in forward_request
    modified_request = transform_template(req_data)
  File "/opt/code/localstack/localstack/services/cloudformation/cloudformation_listener.py", line 83, in transform_template
    if parsed.get('Transform') == 'AWS::Serverless-2016-10-31':
AttributeError: 'str' object has no attribute 'get'`

Although, when I try the **list-stacks** api it seems to be working fine
`aws --endpoint-url=http://localhost:4581 cloudformation list-stacks`

`{
    "StackSummaries": []
}`

`2019-12-31 22:10:51,865:API: 127.0.0.1 - - [31/Dec/2019 22:10:51] "GET / HTTP/1.1" 200 -`

I could not find a solution in any of the past issues or anywhere on the internet. Please assist
LOG.debug('Extract resource attribute: %s %s' % (resource_type, attribute))
    
    if resource_type == 'Lambda::Function':
        actual_attribute = 'FunctionArn' if attribute == 'Arn' else attribute
        return resource['Configuration'][actual_attribute]
    elif resource_type == 'DynamoDB::Table':
        actual_attribute = 'LatestStreamArn' if attribute == 'StreamArn' else attribute
        value = resource['Table'].get(actual_attribute)
        return value
    elif resource_type == 'ApiGateway::RestApi':
        if attribute == 'PhysicalResourceId':
            return resource['id']
        if attribute == 'RootResourceId':
            resources = aws_stack.connect_to_service('apigateway').get_resources(restApiId=resource['id'])['items']
            for res in resources:
                if res['path'] == '/' and not res.get('parentId'):
                    return res['id']
    elif resource_type == 'ApiGateway::Resource':
        if attribute == 'PhysicalResourceId':
            return resource['id']
    attribute_lower = common.first_char_to_lower(attribute)
    return resource.get(attribute) or resource.get(attribute_lower)
def resolve_ref(stack_name, ref, resources, attribute):
    if ref == 'AWS::Region':
        return aws_stack.get_region()
    if ref == 'AWS::Partition':
        return 'aws'
    if ref == 'AWS::StackName':
        return stack_name