With reference to news group thread https://groups.google.com/forum/#!topic/rodauth/MOBVSp2z-Qg
The code to trigger the error is commented inside roauth confg block in app.rb file.
$ rackup # development mode
or
$ ./prod.sh # production mode
go to http://localhost:9292/login.
$ tree
.
├── app.rb
├── config.ru
├── db.rb
├── Gemfile
├── Gemfile.lock
├── migrate
│ └── 001_tables.rb
├── prod.sh
├── README.org
└── views
├── home
│ └── index.erb
└── layouts
├── default.erb
├── _head.erb
├── _nav.erb
└── session.erb