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
import base64
import logging
import zipfile
import threading
import traceback
import hashlib
from io import BytesIO
from datetime import datetime
from six.moves import cStringIO as StringIO
from six.moves.urllib.parse import urlparse
from flask import Flask, Response, jsonify, request
from localstack import config
from localstack.constants import TEST_AWS_ACCOUNT_ID
from localstack.services import generic_proxy
from localstack.services.awslambda import lambda_executors
from localstack.services.awslambda.lambda_executors import (
    LAMBDA_RUNTIME_PYTHON27,
    LAMBDA_RUNTIME_PYTHON36,
    LAMBDA_RUNTIME_NODEJS,
    LAMBDA_RUNTIME_NODEJS610,
    LAMBDA_RUNTIME_NODEJS810,
    LAMBDA_RUNTIME_JAVA8,
    LAMBDA_RUNTIME_DOTNETCORE2,
    LAMBDA_RUNTIME_DOTNETCORE21,
    LAMBDA_RUNTIME_GOLANG,
    LAMBDA_RUNTIME_RUBY,
    LAMBDA_RUNTIME_RUBY25,
    LAMBDA_RUNTIME_CUSTOM_RUNTIME)
from localstack.utils.common import (to_str, load_file, save_file, TMP_FILES, ensure_readable,
    mkdir, unzip, is_zip_file, run, short_uid, is_jar_archive, timestamp, TIMESTAMP_FORMAT_MILLIS,