octane / module unification support

I did:
```
npm install -g https://github.com/ember-cli/ember-cli.git
ember new ember-app --blueprint module-unification-app --yarn
ember install ember-paper
```

I moved app/styles/app.scss to ui/styles/app.scss

Got this error
```
Build Error (SassCompiler)

File not found: /app/styles/app.scss
in any of the following include paths:
/home/me/Development/tmp/ember-app/tmp/sass_compiler-input_base_path-HrmUtsmg.tmp

Stack Trace and Error Report: /tmp/error.dump.d82574aad036cdf57a0561a8215102dc.log
```

So, I moved the file back to app/styles/app.scss, and the problem/error was the exact same.
I even tried the steps again without moving the defaultly generated file.