sqs.changeMessageVisibility according to [this](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_ChangeMessageVisibility.html#API_ChangeMessageVisibility_Examples) makes a request directly to the Queue's URL rather than via the SQS Endpoint. (I'm already setting SQS endpoint to LOCALSTACK_HOSTNAME - makes no difference for this call)..

In localstack the queue URL host returned is by default set to the value of HOSTNAME_EXTERNAL, which I'm setting to localstack, but calling this method within a lambda, does not work and I get the error:

```
UnknownEndpoint: Inaccessible host: `localstack'. This service may not be available in the `us-east-1' region. 
```

So, how can I make the queue URL accessible from within a lambda using localstack? Effectively I need to make **http://localstack** accessible from within lambda.

I'm using the following cmd to start localstack:

```
LAMBDA_EXECUTOR=docker-reuse DEBUG=1 LAMBDA_REMOTE_DOCKER=0 DATA_DIR=/tmp/localstack/data HOSTNAME_EXTERNAL=localstack localstack start
```
arn = func_arn(lambda_name)
        if arn in arn_to_lambda:
            return error_response('Function already exist: %s' %
                lambda_name, 409, error_type='ResourceConflictException')
        arn_to_lambda[arn] = func_details = LambdaFunction(arn)
        func_details.versions = {'$LATEST': {'RevisionId': str(uuid.uuid4())}}
        func_details.last_modified = isoformat_milliseconds(datetime.utcnow()) + '+0000'
        func_details.description = data.get('Description', '')
        func_details.handler = data['Handler']
        func_details.runtime = data['Runtime']
        func_details.envvars = data.get('Environment', {}).get('Variables', {})
        func_details.tags = data.get('Tags', {})
        func_details.timeout = data.get('Timeout', LAMBDA_DEFAULT_TIMEOUT)
        func_details.role = data['Role']
        func_details.memory_size = data.get('MemorySize')
        func_details.code = data['Code']
        func_details.set_dead_letter_config(data)
        result = set_function_code(func_details.code, lambda_name)
        if isinstance(result, Response):
            del arn_to_lambda[arn]
            return result
        
        func_details.code.pop('ZipFile', None)
        
        result.update(format_func_details(func_details))
        if data.get('Publish', False):
            result['Version'] = publish_new_function_version(arn)['Version']
        return jsonify(result or {})
    except Exception as e:
        arn_to_lambda.pop(arn, None)