```ruby
require 'bundler'
Bundler.require

use Rack::HTTPLogger
run lambda { [404, {'Content-Type' => 'text/html'}, ['Page Not Found']] }
```

Set .sync to true, so notifications are logged in development
user
```ruby
require 'bundler'
Bundler.require

$stdout.sync = true

use Rack::HTTPLogger
run lambda { [404, {'Content-Type' => 'text/html'}, ['Page Not Found']] }
```
assistant