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
return s3_truncate_result_orig(result_keys, max_keys or 1000)
    s3_truncate_result_orig = s3_responses.S3ResponseInstance._truncate_result
    s3_responses.S3ResponseInstance._truncate_result = types.MethodType(
        s3_truncate_result, s3_responses.S3ResponseInstance)
    
    
    s3_delete_keys_response_template = """<?xml version="1.0" encoding="UTF-8"?>
    <DeleteResult xmlns="http://s3.amazonaws.com/doc/2006-03-01">
    {% for k in deleted %}
    <Deleted>
    <Key>{{k.key}}</Key>
    <VersionId>{{k.version_id}}</VersionId>
    </Deleted>
    {% endfor %}
    {% for k in delete_errors %}
    <Error>
    <Key>{{k}}</Key>
    </Error>
    {% endfor %}
    </DeleteResult>"""
    def s3_bucket_response_delete_keys(self, request, body, bucket_name):
        template = self.response_template(s3_delete_keys_response_template)
        elements = minidom.parseString(body).getElementsByTagName('Object')
        if len(elements) == 0: