# 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.
return jsonify(do_update_alias(arn, name, version, description))
@app.route('%s/functions/<function>/aliases/<name>' % PATH_ROOT, methods=['GET'])
def get_alias(function, name):
    arn = func_arn(function)
    if arn not in arn_to_lambda:
        return not_found_error(arn)
    if name not in arn_to_lambda.get(arn).aliases:
        return not_found_error(msg='Alias not found: %s:%s' % (arn, name))
    return jsonify(arn_to_lambda.get(arn).aliases.get(name))
@app.route('%s/functions/<function>/aliases' % PATH_ROOT, methods=['GET'])
def list_aliases(function):
    arn = func_arn(function)
    if arn not in arn_to_lambda:
        return not_found_error(arn)
    return jsonify({'Aliases': sorted(arn_to_lambda.get(arn).aliases.values(),
                                      key=lambda x: x['Name'])})
@app.route('/<version>/functions/<function>/concurrency', methods=['PUT'])
def put_concurrency(version, function):
    
    
    
    arn = func_arn(function)
    data = json.loads(request.data)
    lambda_details = arn_to_lambda.get(arn)
    if not lambda_details:
        return not_found_error(arn)
    lambda_details.concurrency = data
    return jsonify(data)
@app.route('/<version>/tags/<arn>', methods=['GET'])
def list_tags(version, arn):