module unification app with relative @import LESS files won't build

[ghost]

I recently ran the ember-module-migrator to migrate our app to the improved structure.
ember build fails because of a LESS Compiler error:

Build Canceled: Broccoli Builder ran into an error with `LessCompiler` plugin. 💥
'routes/some-route.less' wasn't found.

Our app uses relative LESS imports like so:

// line from src/ui/styles/app.less
// these files exist in src/ui/styles/routes
@import "routes/some-route.less";

This relates to emberjs/ember.js#16373

[knownasilya]

Closing since MU was discontinued for smaller incremental changes