The following example `serverless.yml` fails to deploy on localstack:

```yaml
service: "localtest"

provider:
  name: "aws"
  runtime: "nodejs10.x"

functions:
  hello:
    handler: "handler.hello"
    
resources:
  Resources:
    ApiGatewayRestApi:
      Type: "AWS::ApiGateway::RestApi"
      Properties:
        Name: "${self:provider.stage}-${self:service}"
    GatewayResponseDefault400:
      Type: "AWS::ApiGateway::GatewayResponse"
      Properties:
        RestApiId:
          Ref: "ApiGatewayRestApi"
        ResponseType: "DEFAULT_4XX"
        ResponseTemplates:
          application/json: '{"errors":[{"message":"Custom text."}]}'
    GatewayResponseUnauthorized:
      Type: "AWS::ApiGateway::GatewayResponse"
      Properties:
        RestApiId:
          Ref: "ApiGatewayRestApi"
        ResponseType: "UNAUTHORIZED"
        ResponseTemplates:
          application/json: '{"errors":[{"message":"Custom text!", "extra":"Some extra info"}]}'
    GatewayResponseDefault500:
      Type: "AWS::ApiGateway::GatewayResponse"
      Properties:
        RestApiId:
          Ref: "ApiGatewayRestApi"
        ResponseType: "DEFAULT_5XX"
        ResponseTemplates:
          application/json: '{"errors":[{"message":$context.error.messageString}]}'
    GatewayResponseIntegrationTimeout:
      Type: "AWS::ApiGateway::GatewayResponse"
      Properties:
        RestApiId:
          Ref: "ApiGatewayRestApi"
        ResponseType: "INTEGRATION_TIMEOUT"
        ResponseTemplates:
          application/json: '{"errors":[{"message":$context.error.messageString}]}'

plugins:
- "serverless-localstack"

custom:
  localstack:
    stages:
      - "local"
```

The error on the localstack end is `Exception: CloudFormation deployment for resource type ApiGateway::GatewayResponse not yet implemented`.
from pympler import muppy, summary
        all_objects = muppy.get_objects()
        result = summary.summarize(all_objects)
        result = result[0:20]
        summary = '\n'.join([l for l in summary.format_(result)])
        result = '%s\n\n%s' % (summary, json.dumps(result))
        return result, 200, {'content-type': 'text/plain'}
    def create_backend_app(service):
        backend_app = moto_server.create_backend_app_orig(service)
        backend_app.add_url_rule(
            '/_stats', endpoint='_get_stats', methods=['GET'], view_func=_get_stats, strict_slashes=False)
        return backend_app
    if not hasattr(moto_server, 'create_backend_app_orig'):
        moto_server.create_backend_app_orig = moto_server.create_backend_app
        moto_server.create_backend_app = create_backend_app
def start_up(*args):
    
    apply_patches()
    
    inject_stats_endpoint()
    return moto_main(*args)
def main():
    setup_logging()
    
    canonicalize_api_names()
    
    sys.exit(start_up())
if __name__ == '__main__':
    main()