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
```
"""Add Last-Modified header with current time
    (if the response content is an XML containing <LastModified>, add that instead)"""
    time_format = '%a, %d %b %Y %H:%M:%S GMT'  
    try:
        if content:
            last_modified_str = re.findall(r'<LastModified>([^<]*)</LastModified>', content)
            if last_modified_str:
                last_modified_str = last_modified_str[0]
                last_modified_time_format = dateutil.parser.parse(last_modified_str).strftime(time_format)
                response.headers['Last-Modified'] = last_modified_time_format
    except TypeError as err:
        LOGGER.debug('No parsable content: %s' % err)
    except ValueError as err:
        LOGGER.error('Failed to parse LastModified: %s' % err)
    except Exception as err:
        LOGGER.error('Caught generic exception (parsing LastModified): %s' % err)
    
    try:
        if response.headers.get('Last-Modified', '') == '':
            response.headers['Last-Modified'] = datetime.datetime.now().strftime(time_format)
    except Exception as err:
        LOGGER.error('Caught generic exception (setting LastModified header): %s' % err)
def append_list_objects_marker(method, path, data, response):