Guys,

I've started using Localstack recently and loving it so far. I've ran into an issue and can't figure out what I am missing in my configuration if there is any.

So, i've managed to configure and test the following successfully

1.  `
API GW --> SQS` - If I post a message to the HTTP Endpoint it gets to SQS and I see SQS response (Default SQS style, i.e SendMessageResponse XML)

2. `SQS --> Lambda` - If I post a message into SQS manually, then corresponding Lambda gets triggered (I see Lambda logs) and I see SQS response (Default SQS style, i.e SendMessageResponse XML)

But If I combine these two i.e

`API GW --> SQS --> Lambda` - then

- I see Lambda is being excuted (i see lambda logs  exactly how they are in 2 above)
- But don't get SQS response (Default SQS style, i.e SendMessageResponse XML)
- Following exception is being thrown

```
localstack_1  | 2019-09-25T14:09:53:ERROR:localstack.services.generic_proxy: Error forwarding request: object supporting the buffer API required Traceback (most recent call last):
localstack_1  |   File "/opt/code/localstack/localstack/services/generic_proxy.py", line 239, in forward
localstack_1  |     path=path, data=data, headers=forward_headers)
localstack_1  |   File "/opt/code/localstack/localstack/services/sqs/sqs_listener.py", line 49, in forward_request
localstack_1  |     new_response = self._send_message(path, data, req_data, headers)
localstack_1  |   File "/opt/code/localstack/localstack/services/sqs/sqs_listener.py", line 237, in _send_message
localstack_1  |     message_attr_hash=md5(data),
localstack_1  |   File "/opt/code/localstack/localstack/utils/common.py", line 304, in md5
localstack_1  |     m.update(to_bytes(string))
localstack_1  | TypeError: object supporting the buffer API required
```

`Implement API Gateway SQS proxy` is recently implented with PR https://github.com/localstack/localstack/pull/1354 (Thanks to @mathewpower )

and I'm wondering is this anything to do with missing `data=` parameter at 
https://github.com/mathewpower/localstack/blob/028cc8660317aac426c1195ba7d8dedf45ef9007/localstack/services/apigateway/apigateway_listener.py#L86

Really appreciate your help on this.

Thanks 

result = requests.get(url)
        self.assertEqual(result.status_code, 200)
        self.assertEqual(to_str(result.content), '{}')
        data = {'data': 123}
        result = requests.post(url, data=json.dumps(data))
        self.assertEqual(result.status_code, 200)
        self.assertEqual(json.loads(to_str(result.content)), data)
        
        proxy.stop()
    def test_api_gateway_lambda_proxy_integration(self):
        self._test_api_gateway_lambda_proxy_integration(
            self.TEST_LAMBDA_PROXY_BACKEND,
            self.API_PATH_LAMBDA_PROXY_BACKEND)
    def test_api_gateway_lambda_proxy_integration_with_path_param(self):
        self._test_api_gateway_lambda_proxy_integration(
            self.TEST_LAMBDA_PROXY_BACKEND_WITH_PATH_PARAM,
            self.API_PATH_LAMBDA_PROXY_BACKEND_WITH_PATH_PARAM)
    def _test_api_gateway_lambda_proxy_integration(self, fn_name, path):
        
        zip_file = testutil.create_lambda_archive(
            load_file(TEST_LAMBDA_PYTHON),
            get_content=True,
            libs=TEST_LAMBDA_LIBS,
            runtime=LAMBDA_RUNTIME_PYTHON27
        )
        testutil.create_lambda_function(
            func_name=fn_name,
            zip_file=zip_file,
            runtime=LAMBDA_RUNTIME_PYTHON27
        )