Devise.add_mapping adds a dependency on Rails

[Gurpartap]

When I add Devise.add_mapping(:users, {}), it errors out with:

.bundle/ruby/2.2.0/gems/devise-3.5.1/lib/devise/failure_app.rb:13:in
`<class:FailureApp>': undefined method `routes' for nil:NilClass (NoMethodError)

Line 13 of devise's failure_app.rb is include Rails.application.routes.url_helpers.

Perhaps it's inadvertently adding a dependency to Rails here. Is there a way to avoid this?