```ruby
module Committee::Middleware
  class Base
    def initialize(app, options={})
      @app = app

      @params_key = options[:params_key] || "committee.params"
      data = options[:schema] || raise("need option `schema`")
      if data.is_a?(String)
        warn_string_deprecated
        data = MultiJson.decode(data)
      end
      @schema = JsonSchema.parse!(data)
      @schema.expand_references!
      @router = Committee::Router.new(@schema)
    end

    private

    def render_error(status, id, message)
      [status, { "Content-Type" => "application/json" },
        [MultiJson.encode({ id: id, error: message }, pretty: true)]]
    end

    def warn_string_deprecated
      Committee.warn_deprecated("Committee: passing a string to `schema` option is deprecated; please send a deserialized hash instead.")
    end
  end
end
```

Use `message` field instead of error
user
```ruby
module Committee::Middleware
  class Base
    def initialize(app, options={})
      @app = app

      @params_key = options[:params_key] || "committee.params"
      data = options[:schema] || raise("need option `schema`")
      if data.is_a?(String)
        warn_string_deprecated
        data = MultiJson.decode(data)
      end
      @schema = JsonSchema.parse!(data)
      @schema.expand_references!
      @router = Committee::Router.new(@schema)
    end

    private

    def render_error(status, id, message)
      [status, { "Content-Type" => "application/json" },
        [MultiJson.encode({ id: id, message: message }, pretty: true)]]
    end

    def warn_string_deprecated
      Committee.warn_deprecated("Committee: passing a string to `schema` option is deprecated; please send a deserialized hash instead.")
    end
  end
end
```
assistant