Regex in route scope breaks _path_template methods

[cavis]

Adding a constraint to a routes.rb scope breaks the path template helper methods:

scope ':api_version', api_version: /v1|v2/ do

... later

api_story_path_template(api_version: represented.version, id: '{id}')

... throws

ActionController::UrlGenerationError (No route matches {:action=>"show", :api_version=>"_API_VERSION_REPLACE_", :controller=>"api/stories", :id=>"_ID_REPLACE_"} missing required keys: [:api_version]):
  app/representers/api/api_representer.rb:17:in `block in <class:ApiRepresenter>'
  app/controllers/api/api_responder.rb:14:in `api_behavior'
  app/controllers/api/base_controller.rb:35:in `entrypoint'

Appears to be due to how uri_methods.rb replaces the "v1" version string with the placeholder "_API_VERSION_REPLACE_" ... which doesn't match the regex.