unable to generate local rdocs?

Currently if I do a gem fetch rails, gem unpack xxx.gem
cd xxx
rake rdoc

I get this:

Generating HTML...
Could not find HTML template '../doc/template/horo'

and the doc file remains empty. Is this expected?
Thank you.

By trial and error I had the impression that some Rakefiles have doc
tasks that are obsolete or perhaps need something that is not in the

For a single gem you can get something via the rdoc command.

Publishing the public API is the job of release.rb. The tasks involved
there do work, as long as you have the Jamis template and an RDoc
older than 2.4. We are working on bringing the API to RDoc 2.4, more
to come about this.