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`.
if uri.startswith('arn:aws:apigateway:') and ':lambda:path' in uri:
            func_arn = uri.split(':lambda:path')[1].split('functions/')[1].split('/invocations')[0]
            data_str = json.dumps(data) if isinstance(data, (dict, list)) else data
            account_id = uri.split(':lambda:path')[1].split(':function:')[0].split(':')[-1]
            source_ip = headers['X-Forwarded-For'].split(',')[-2]
            
            
            request_context = {
                'path': relative_path,
                'accountId': account_id,
                'resourceId': resource.get('id'),
                'stage': stage,
                'identity': {
                    'accountId': account_id,
                    'sourceIp': source_ip,
                    'userAgent': headers['User-Agent'],
                }
            }
            try:
                path_params = extract_path_params(path=relative_path, extracted_path=extracted_path)
            except Exception:
                path_params = {}
            result = lambda_api.process_apigateway_invocation(func_arn, relative_path, data_str,
                headers, path_params=path_params, query_string_params=query_string_params,
                method=method, resource_path=path, request_context=request_context)
            if isinstance(result, FlaskResponse):
                return flask_to_requests_response(result)
            if isinstance(result, Response):
                return result
            response = Response()