Rhapsody server templates are now written in EJS. If you are working with Rhapsody's server templates, you will immediately notice that the Pug files are gone. EJS is a templating language (much like ERB in Ruby or EEX files in Elixir) that embeds JS expressions inside other file types, HTML files in Rhapsody's case. Rhapsody's templates are now much more similar in syntax to the HTML files they will eventually become. This change also simplifies some upcoming server infrastructure work as we continue to simplify Rhapsody's production environment.
See the EJS website for more information on EJS itself.