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
```
LAMBDA_DEFAULT_RUNTIME = LAMBDA_RUNTIME_PYTHON36
LAMBDA_DEFAULT_STARTING_POSITION = 'LATEST'
LAMBDA_ZIP_FILE_NAME = 'original_lambda_archive.zip'
LAMBDA_JAR_FILE_NAME = 'original_lambda_archive.jar'
DEFAULT_BATCH_SIZE = 10
app = Flask(APP_NAME)
arn_to_lambda = {}
event_source_mappings = []
LOG = logging.getLogger(__name__)
exec_mutex = threading.Semaphore(1)
DO_USE_DOCKER = None
JSON_START_CHAR_MAP = {
    list: ('[',),
    tuple: ('[',),
    dict: ('{',),
    str: ('"',),
    bytes: ('"',),
    bool: ('t', 'f'),
    type(None): ('n',),
    int: ('0', '1', '2', '3', '4', '5', '6', '7', '8', '9'),
    float: ('0', '1', '2', '3', '4', '5', '6', '7', '8', '9')
}
POSSIBLE_JSON_TYPES = (str, bytes)
JSON_START_TYPES = tuple(set(JSON_START_CHAR_MAP.keys()) - set(POSSIBLE_JSON_TYPES))
JSON_START_CHARS = tuple(set(functools.reduce(lambda x, y: x + y, JSON_START_CHAR_MAP.values())))
LAMBDA_EXECUTOR = lambda_executors.AVAILABLE_EXECUTORS.get(config.LAMBDA_EXECUTOR, lambda_executors.DEFAULT_EXECUTOR)
IAM_POLICY_VERSION = '2012-10-17'
POLICY_NAME_PATTERN = 'lambda_policy_%s'
BUCKET_MARKER_LOCAL = '__local__'
class ClientError(Exception):