# Steps to reproduce

* Start `localstack` (version 0.10.3).
* Don't create any lambda functions.
* Run:

```sh
AWS_ACCESS_KEY_ID='a' AWS_SECRET_ACCESS_KEY='b' \
aws lambda invoke \
  --function-name 'my-func' \
  --qualifier='qual' \
  --endpoint http://localhost:4574 test.out
```

* Expected behaviour — a `ResourceNotFoundException` from `aws-cli`.
* Actual behaviour — `An error occurred (500) when calling the Invoke operation` message and a 500 response.

This bug only appears if a `qualifier` is included in the request.
try:
        queue_arn = aws_stack.sqs_queue_arn(queue_name, region_name=region_name)
        sources = get_event_sources(source_arn=queue_arn)
        LOG.debug('Found %s source mappings for event from SQS queue %s' % (len(sources), queue_arn))
        source = next(iter(sources), None)
        if source:
            arn = source['FunctionArn']
            event = {'Records': [{
                'body': message_body,
                'receiptHandle': 'MessageReceiptHandle',
                'md5OfBody': md5(message_body),
                'eventSourceARN': queue_arn,
                'eventSource': 'aws:sqs',
                'awsRegion': region_name,
                'messageId': str(uuid.uuid4()),
                'attributes': {
                    'ApproximateFirstReceiveTimestamp': '{}000'.format(int(time.time())),
                    'SenderId': TEST_AWS_ACCOUNT_ID,
                    'ApproximateReceiveCount': '1',
                    'SentTimestamp': '{}000'.format(int(time.time()))
                },
                'messageAttributes': message_attributes,
                'sqs': True,
            }]}
            run_lambda(event=event, context={}, func_arn=arn)
            return True
    except Exception as e:
        LOG.warning('Unable to run Lambda function on SQS messages: %s %s' % (e, traceback.format_exc()))
def get_event_sources(func_name=None, source_arn=None):