[3.3.3 Regression] @extend #{'%test'} !optional errors

[eoneill]

Given...

.test {
  @extend #{'%test'} !optional
}

fails (as of v3.3.3) with error:

The selector "%test" was not found.
Use "@extend %test !optional" if the extend should be able to fail.

using:

node-sass   3.5.0-beta.1    (Wrapper)   [JavaScript]
libsass     3.3.3   (Sass Compiler) [C/C++]

However, the above works as expected (no error) when using v3.3.2:

node-sass   3.4.2   (Wrapper)   [JavaScript]
libsass     3.3.2   (Sass Compiler) [C/C++]