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
s3_models.DEFAULT_KEY_BUFFER_SIZE = S3_MAX_FILE_SIZE_MB * 1024 * 1024
    def init(self, name, value, storage='STANDARD', etag=None,
            is_versioned=False, version_id=0, max_buffer_size=None, *args, **kwargs):
        return original_init(self, name, value, storage=storage, etag=etag, is_versioned=is_versioned,
            version_id=version_id, max_buffer_size=s3_models.DEFAULT_KEY_BUFFER_SIZE, *args, **kwargs)
    original_init = s3_models.FakeKey.__init__
    s3_models.FakeKey.__init__ = init
    def s3_update_acls(self, request, query, bucket_name, key_name):
        
        
        acl_key = 'acl|%s|%s' % (bucket_name, key_name)
        acl = self._acl_from_headers(request.headers)
        if acl:
            TMP_STATE[acl_key] = acl
        if not query.get('uploadId'):
            return
        bucket = self.backend.get_bucket(bucket_name)
        key = bucket and self.backend.get_key(bucket_name, key_name)
        if not key:
            return
        acl = acl or TMP_STATE.pop(acl_key, None) or bucket.acl
        if acl:
            key.set_acl(acl)
    
    @classmethod
    def Bucket_create_from_cloudformation_json(cls, resource_name, cloudformation_json, region_name):