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`.
updated_response = self.proxy.update_listener.return_response(**kwargs)
                if isinstance(updated_response, Response):
                    response = updated_response
            
            self.send_response(response.status_code)
            content_length_sent = False
            for header_key, header_value in iteritems(response.headers):
                
                if header_key.lower() not in ('transfer-encoding', 'date', 'server'):
                    self.send_header(header_key, header_value)
                    content_length_sent = content_length_sent or header_key.lower() == 'content-length'
            if not content_length_sent:
                self.send_header('Content-Length', '%s' % len(response.content) if response.content else 0)
            
            self._send_cors_headers(response)
            self.end_headers()
            if response.content and len(response.content):
                self.wfile.write(to_bytes(response.content))
        except Exception as e:
            trace = str(traceback.format_exc())
            conn_errors = ('ConnectionRefusedError', 'NewConnectionError',
                           'Connection aborted', 'Unexpected EOF', 'Connection reset by peer')
            conn_error = any(e in trace for e in conn_errors)
            error_msg = 'Error forwarding request: %s %s' % (e, trace)
            if 'Broken pipe' in trace:
                LOG.warn('Connection prematurely closed by client (broken pipe).')
            elif not self.proxy.quiet or not conn_error:
                LOG.error(error_msg)
                if os.environ.get(ENV_INTERNAL_TEST_RUN):