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`.
self.request = request
        self.client_address = client_address
        self.server = server
        self.proxy = server.my_object
        self.data_bytes = None
        self.protocol_version = self.proxy.protocol_version
        try:
            BaseHTTPRequestHandler.__init__(self, request, client_address, server)
        except SSLError as e:
            LOG.warning('SSL error when handling request: %s' % e)
    def parse_request(self):
        result = BaseHTTPRequestHandler.parse_request(self)
        if not result:
            return result
        if sys.version_info[0] >= 3:
            return result
        
        
        expect = self.headers.get('Expect', '')
        if (expect.lower() == '100-continue' and
                self.protocol_version >= 'HTTP/1.1' and
                self.request_version >= 'HTTP/1.1'):
            if self.request_version != 'HTTP/0.9':
                self.wfile.write(('%s %d %s\r\n' %
                    (self.protocol_version, 100, 'Continue')).encode('latin1', 'strict'))
                self.end_headers()
        return result
    def do_GET(self):