Cannot use scope package for theme. #360

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Bug report

You can't use a scoped package as a theme. If you try to set one, you get the following error:

error Error: Cannot find module 'saber-theme-@skewedaspect/saber-theme-minima/package.json'
Require stack:
- /Users/ccase/devel/armtech/saber-test/docs/noop.js
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:623:15)
    at resolveFileName (/Users/ccase/devel/armtech/saber-test/node_modules/saber/node_modules/resolve-from/index.js:29:39)
    at resolveFrom (/Users/ccase/devel/armtech/saber-test/node_modules/saber/node_modules/resolve-from/index.js:43:9)
    at module.exports (/Users/ccase/devel/armtech/saber-test/node_modules/saber/node_modules/resolve-from/index.js:46:47)
    at module.exports (/Users/ccase/devel/armtech/saber-test/node_modules/saber/lib/utils/resolvePackage.js:19:5)
    at Saber.prepare (/Users/ccase/devel/armtech/saber-test/node_modules/saber/lib/index.js:135:20)
    at processTicksAndRejections (internal/process/task_queues.js:89:5)
    at async Saber.serve (/Users/ccase/devel/armtech/saber-test/node_modules/saber/lib/index.js:349:5)
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

Process finished with exit code 1

Version

v0.7.0

Steps to reproduce

Easiest way to reproduce:

• https://github.com/Morgul/saber-scope-bug

Basically, just try to use a theme published under a scoped package.

What is expected?

The theme just works.

What is actually happening?

It does not work.

Other relevant information

• Result of running saber -v:
  • saber/0.7.0 darwin-x64 node-v12.4.0
• Is Saber a global or local install?
  • local
• Which package manager did you use for the install?
  • yarn
• Does this issue occur when all plugins are disabled?
  • yes