Shows

Errno::ENOENT at /
No such file or directory - /home/david/.rbenv/versions/1.9.3-p448/lib/ruby/gems/1.9.1/gems/nesta-0.9.13/views/index.haml

instead of

LoadError: cannot load such file -- ...

Come across that bug when forgot to bundle or had a typo in require statements. Instead of showing LoadError it just ignores the whole custom app.rb in my app directory.