'rake' doesn't work if 'rvm' is not installed

I see the following:

$ rake --tasks
rake aborted!
No such file or directory - rvm
/src/ws/baserock/me/import-rails/checkouts/ruby-gems_builder/rakelib/tags.rake:15:in ``'
/src/ws/baserock/me/import-rails/checkouts/ruby-gems_builder/rakelib/tags.rake:15:in `<module:Tags>'
/src/ws/baserock/me/import-rails/checkouts/ruby-gems_builder/rakelib/tags.rake:3:in `<top (required)>'
(See full trace by running task with --trace)