Hi, I'm trying to set up the ApiGateway Lambda Authorizer but it looks like it doesn't work yet

Terraform code: 
```
resource "aws_api_gateway_authorizer" "demo" {
  name                   = "demo"
  rest_api_id            = "${aws_api_gateway_rest_api.demo.id}"
  authorizer_uri         = "${aws_lambda_function.authorizer.invoke_arn}"
  authorizer_credentials = "${aws_iam_role.invocation_role.arn}"
  type = "TOKEN"
}

resource "aws_api_gateway_rest_api" "demo" {
  name = "auth-demo"
}

resource "aws_iam_role" "invocation_role" {
  name = "api_gateway_auth_invocation"
  path = "/"

  assume_role_policy = <<EOF
...
EOF
}

resource "aws_iam_role_policy" "invocation_policy" {
  name = "default"
  role = "${aws_iam_role.invocation_role.id}"

  policy = <<EOF
...
EOF
}

resource "aws_iam_role" "lambda" {
  name = "demo-lambda"

  assume_role_policy = <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
...
}

resource "aws_lambda_function" "authorizer" {
  filename      = "${var.lambda_auth}"
  function_name = "api_gateway_authorizer"
  role          = "${aws_iam_role.lambda.arn}"
  handler       = "src/script.lambda_handler"
  runtime       = "python3.7"
  source_code_hash = "${filebase64sha256("${var.lambda_auth}")}"
}
```


I'm getting this on the debug logs:

```
Traceback (most recent call last):
  File "/opt/code/localstack/.venv/lib/python3.7/site-packages/werkzeug/serving.py", line 304, in run_wsgi
    execute(self.server.app)
  File "/opt/code/localstack/.venv/lib/python3.7/site-packages/werkzeug/serving.py", line 292, in execute
    application_iter = app(environ, start_response)
  File "/opt/code/localstack/.venv/lib/python3.7/site-packages/moto/server.py", line 132, in __call__
    return backend_app(environ, start_response)
  File "/opt/code/localstack/.venv/lib/python3.7/site-packages/flask/app.py", line 2309, in __call__
    return self.wsgi_app(environ, start_response)
  File "/opt/code/localstack/.venv/lib/python3.7/site-packages/flask/app.py", line 2295, in wsgi_app
    response = self.handle_exception(e)
  File "/opt/code/localstack/.venv/lib/python3.7/site-packages/flask_cors/extension.py", line 161, in wrapped_function
    return cors_after_request(app.make_response(f(*args, **kwargs)))
  File "/opt/code/localstack/.venv/lib/python3.7/site-packages/flask/app.py", line 1741, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/opt/code/localstack/.venv/lib/python3.7/site-packages/flask/_compat.py", line 35, in reraise
    raise value
  File "/opt/code/localstack/.venv/lib/python3.7/site-packages/flask/app.py", line 2292, in wsgi_app
    response = self.full_dispatch_request()
  File "/opt/code/localstack/.venv/lib/python3.7/site-packages/flask/app.py", line 1815, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/opt/code/localstack/.venv/lib/python3.7/site-packages/flask_cors/extension.py", line 161, in wrapped_function
    return cors_after_request(app.make_response(f(*args, **kwargs)))
  File "/opt/code/localstack/.venv/lib/python3.7/site-packages/flask/app.py", line 1718, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/opt/code/localstack/.venv/lib/python3.7/site-packages/flask/_compat.py", line 35, in reraise
    raise value
  File "/opt/code/localstack/.venv/lib/python3.7/site-packages/flask/app.py", line 1813, in full_dispatch_request
    rv = self.dispatch_request()
  File "/opt/code/localstack/.venv/lib/python3.7/site-packages/flask/app.py", line 1799, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/opt/code/localstack/.venv/lib/python3.7/site-packages/moto/core/utils.py", line 142, in __call__
    if len(result) == 3:
TypeError: object of type 'NoneType' has no len()
```

And sometimes this in terraform

`Error: error waiting for Lambda Function (api_gateway_authorizer) creation: unexpected state '', wanted target 'Active'. last error: %!s(<nil>)`

Is this feature available yet ? Thank you
---
        operationId: 'invokeFunction'
        parameters:
            - name: 'request'
              in: body
    """
    
    arn = func_arn(function)
    
    m = re.match('(arn:aws:lambda:.*:.*:function:[a-zA-Z0-9-_]+)(:.*)?', arn)
    if m and m.group(2):
        qualifier = m.group(2)[1:]
        arn = m.group(1)
    else:
        qualifier = request.args.get('Qualifier')
    data = request.get_data()
    if data:
        data = to_str(data)
        try:
            data = json.loads(data)
        except Exception:
            try:
                
                data = json.loads(parse_chunked_data(data))
            except Exception:
                return error_response('The payload is not JSON: %s' % data, 415,
                                      error_type='UnsupportedMediaTypeException')
    
    invocation_type = request.environ.get('HTTP_X_AMZ_INVOCATION_TYPE', 'RequestResponse')
    def _create_response(result, status_code=200):