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`.
resource_type = get_resource_type(resource)
    entry = RESOURCE_TO_FUNCTION.get(resource_type)
    if entry is None:
        LOG.warning('Unknown resource type "%s": %s' % (resource_type, resource))
    return bool(entry and entry.get(ACTION_CREATE))
def is_deployed(resource_id, resources, stack_name):
    resource = resources[resource_id]
    resource_status = resource.get('__details__') or {}
    details = retrieve_resource_details(resource_id, resource_status, resources, stack_name)
    return bool(details)
def should_be_deployed(resource_id, resources, stack_name):
    """ Return whether the given resource is all of: (1) deployable, (2) not yet deployed,
        and (3) has no unresolved dependencies. """
    resource = resources[resource_id]
    if not is_deployable_resource(resource) or is_deployed(resource_id, resources, stack_name):
        return False
    res_deps = get_resource_dependencies(resource_id, resource, resources)
    return all_dependencies_satisfied(res_deps, stack_name, resources, resource_id)
def is_updateable(resource_id, resources, stack_name):
    """ Return whether the given resource can be updated or not """
    resource = resources[resource_id]
    if not is_deployable_resource(resource) or not is_deployed(resource_id, resources, stack_name):
        return False
    resource_type = get_resource_type(resource)
    return resource_type in UPDATEABLE_RESOURCES
def all_dependencies_satisfied(resources, stack_name, all_resources, depending_resource=None):