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
if isinstance(o, dict):
            for k, v in o.items():
                if v == PLACEHOLDER_RESOURCE_NAME:
                    if 'value' not in resource_name_holder:
                        resource_name_holder['value'] = get_resource_name(resource) or resource_id
                    o[k] = resource_name_holder['value']
        return o
    common.recurse_object(params, fix_placeholders)
    
    params = common.merge_recursive(defaults, params)
    
    for param_key, param_value in dict(params).items():
        if param_value is not None:
            param_value = params[param_key] = resolve_refs_recursively(stack_name, param_value, resources)
        
        if str(param_value).lower() in ['true', 'false']:
            params[param_key] = str(param_value).lower() == 'true'
    
    params = fix_account_id_in_arns(params)
    
    params = convert_data_types(func_details, params)
    
    params = remove_none_values(params)
    
    try:
        LOG.debug('Request for resource type "%s" in region %s: %s %s' % (
            resource_type, aws_stack.get_region(), func_details['function'], params))
        result = function(**params)