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`.
result = clean_json_orig(resource_json, resources_map)
        if isinstance(result, BaseModel):
            if isinstance(resource_json, dict) and 'Ref' in resource_json:
                entity_id = get_entity_id(result, resource_json)
                if entity_id:
                    return entity_id
                LOG.warning('Unable to resolve "Ref" attribute for: %s - %s - %s',
                            resource_json, result, type(result))
        return result
    clean_json_orig = parsing.clean_json
    parsing.clean_json = clean_json
    
    parsing.MODEL_MAP.update(MODEL_MAP)
    
    def parse_and_create_resource(logical_id, resource_json, resources_map, region_name):
        try:
            return _parse_and_create_resource(logical_id, resource_json, resources_map, region_name)
        except Exception as e:
            LOG.error('Unable to parse and create resource "%s": %s %s' %
                      (logical_id, e, traceback.format_exc()))
            raise
    def parse_and_update_resource(logical_id, resource_json, resources_map, region_name):
        try:
            return _parse_and_create_resource(logical_id,
                resource_json, resources_map, region_name, update=True)
        except Exception as e:
            LOG.error('Unable to parse and update resource "%s": %s %s' %
                      (logical_id, e, traceback.format_exc()))
            raise
    def _parse_and_create_resource(logical_id, resource_json, resources_map, region_name, update=False):