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
result = s3_key_response_put_orig(request, body, bucket_name, query, key_name, headers, *args, **kwargs)
        s3_update_acls(self, request, query, bucket_name, key_name)
        return result
    s3_key_response_put_orig = s3_responses.S3ResponseInstance._key_response_put
    s3_responses.S3ResponseInstance._key_response_put = types.MethodType(
        s3_key_response_put, s3_responses.S3ResponseInstance)
    
    def s3_key_response_delete(self, bucket_name, query, key_name, *args, **kwargs):
        
        if query.get('tagging'):
            self._set_action('KEY', 'DELETE', query)
            self._authenticate_and_authorize_s3_action()
            key = self.backend.get_key(bucket_name, key_name)
            key.tags = s3_models.FakeTagging()
            return 204, {}, ''
        result = s3_key_response_delete_orig(bucket_name, query, key_name, *args, **kwargs)
        return result
    s3_key_response_delete_orig = s3_responses.S3ResponseInstance._key_response_delete
    s3_responses.S3ResponseInstance._key_response_delete = types.MethodType(
        s3_key_response_delete, s3_responses.S3ResponseInstance)
    s3_responses.ACTION_MAP['KEY']['DELETE']['tagging'] = 'DeleteObjectTagging'
    
    def s3_truncate_result(self, result_keys, max_keys):