Imports from `.` no longer working after upgrading >= 0.13.0

[asottile]

Discovered in pre-commit/pre-commit.com#113

Here's a simple test case:

$ tail -n999 scss/*
==> scss/main.scss <==
@import 'scss/variables';

==> scss/_variables.scss <==

Before:

$ ~/workspace/pre-commit.github.io/venv/bin/sassc --version
sassc 0.12.3 (sass/libsass 3.4.3)
$ ~/workspace/pre-commit.github.io/venv/bin/sassc scss/main.scss out/out.css
$ echo $?
0

After:

$ ~/workspace/pre-commit.github.io/venv/bin/sassc --version
sassc 0.13.0 (sass/libsass 3.4.4)
$ ~/workspace/pre-commit.github.io/venv/bin/sassc scss/main.scss out/out.css
sassc: error: Error: File to import not found or unreadable: scss/variables.
       Parent style sheet: /tmp/foo/scss/main.scss
        on line 1 of scss/main.scss
>> @import 'scss/variables';
   ^

[asottile]

I'm manually bisecting, my first guesses at what changed / broke this were incorrect... I may resort to actual bisection :)

[asottile]

Bumping the submodule back to 3.4.3 fixes it, so it seems to be some behaviour changed between 3.4.3 and 3.4.4

The changelog doesn't seem to indicate anything interesting: https://github.com/sass/libsass/releases/tag/3.4.4

[asottile]

For now, resolved via #209

[asottile]

The fix for this is in 0.13.2