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`.
print('ERROR: %s' % error_msg)
            self.send_response(502)  
            self.end_headers()
            
            self.close_connection = 1
        finally:
            try:
                self.wfile.flush()
            except Exception as e:
                LOG.warning('Unable to flush write file: %s' % e)
    def _send_cors_headers(self, response=None):
        
        headers = response is not None and response.headers or {}
        if 'Access-Control-Allow-Origin' not in headers:
            self.send_header('Access-Control-Allow-Origin', '*')
        if 'Access-Control-Allow-Methods' not in headers:
            self.send_header('Access-Control-Allow-Methods', ','.join(CORS_ALLOWED_METHODS))
        if 'Access-Control-Allow-Headers' not in headers:
            requested_headers = self.headers.get('Access-Control-Request-Headers', '')
            requested_headers = re.split(r'[,\s]+', requested_headers) + CORS_ALLOWED_HEADERS
            self.send_header('Access-Control-Allow-Headers', ','.join([h for h in requested_headers if h]))
        if 'Access-Control-Expose-Headers' not in headers:
            self.send_header('Access-Control-Expose-Headers', ','.join(CORS_EXPOSE_HEADERS))
    def _listeners(self):
        return self.DEFAULT_LISTENERS + [self.proxy.update_listener]
    def log_message(self, format, *args):
        return
class GenericProxy(FuncThread):