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
def attr_val(val):
        return json.dumps(val) if isinstance(val, (dict, list)) else str(val)
    attrs = ['DeliveryPolicy', 'FilterPolicy', 'RawMessageDelivery', 'RedrivePolicy']
    result = dict([(a, attr_val(params[a])) for a in attrs if a in params])
    return result
def select_parameters(*param_names):
    return lambda params, **kwargs: dict([(k, v) for k, v in params.items() if k in param_names])
def dump_json_params(param_func=None, *param_names):
    def replace(params, **kwargs):
        result = param_func(params, **kwargs) if param_func else params
        for name in param_names:
            if isinstance(result.get(name), (dict, list)):
                
                
                param_value = common.json_safe(result[name])
                result[name] = json.dumps(param_value)
        return result
    return replace
def param_defaults(param_func, defaults):
    def replace(params, **kwargs):
        result = param_func(params, **kwargs)
        for key, value in defaults.items():
            if result.get(key) in ['', None]:
                result[key] = value
        return result
    return replace
RESOURCE_TO_FUNCTION = {