Configuring Sass with multiple valid load paths leads to SyntaxError on Windows

[ashmaroli]

Hello Guys 👋

Background

This issue was discovered while migrating Jekyll's built-in sass-converter to use sassc-2.0.0.
Jekyll sites typically have two sass-load-paths pre-configured:

• _sass directory at the site's source root.
• _sass directory at the site's theme root (if the site uses a theme-gem e.g. Minima)

Out-of-the box, a Jekyll site using the sassc branch (the migration PR linked above) yields no errors on both Unix based systems and Windows because the site is only loading sass files from the theme-gem.
The issue arises when the Windows user adds a _sass directory at their site's source root (in order to override styles defined by the theme-gem).

Now there exists two valid entries, in the load_paths array,

Summary

SassC on Windows attempts to import a sass partial from one of the load_paths and just raises instead of checking the other load path for the imported partial as well.

Misc.

• I've a temporary test repo at https://github.com/ashmaroli/sassc-test, wired up with both Travis CI and AppVeyor CI to compare logs across the two platforms.
• This issue is currently preventing the Jekyll Team from migrating to sassc-ruby, and would love your assistance in resolving the issue.
  Thanks.

/cc @am11