Sass 4.0 DEPRECATION WARNING: Passing a string to call()

[fromthestone]

FYI I am trying Jekyll foundation and I got a series of warnings:

DEPRECATION WARNING: Passing a string to call() is deprecated and will be illegal
in Sass 4.0. Use call(get-function("shake")) instead.

DEPRECATION WARNING: Passing a string to call() is deprecated and will be illegal
in Sass 4.0. Use call(get-function("shake")) instead.

DEPRECATION WARNING: Passing a string to call() is deprecated and will be illegal
in Sass 4.0. Use call(get-function("spin")) instead.

DEPRECATION WARNING: Passing a string to call() is deprecated and will be illegal
in Sass 4.0. Use call(get-function("spin")) instead.

DEPRECATION WARNING: Passing a string to call() is deprecated and will be illegal
in Sass 4.0. Use call(get-function("wiggle")) instead.

DEPRECATION WARNING: Passing a string to call() is deprecated and will be illegal
in Sass 4.0. Use call(get-function("wiggle")) instead.

the full log:

% yarn start                                                                                                                                                                                                                                                    19-10-13 - 21:32:35
yarn run v1.19.0
$ gulp
[21:32:57] Using gulpfile ~/dev/test/jekyll-foundation/gulpfile.js
[21:32:57] Starting 'default'...
[21:32:57] Starting 'build'...
[21:32:57] Starting 'clean'...
[21:32:57] Finished 'clean' after 3.47 ms
[21:32:57] Starting 'jekyll-build'...
Configuration file: /Users/mdalmasso/dev/test/jekyll-foundation/_config.yml
            Source: /Users/mdalmasso/dev/test/jekyll-foundation
       Destination: /Users/mdalmasso/dev/test/jekyll-foundation/_site
 Incremental build: enabled
      Generating...
                    done in 0.545 seconds.
 Auto-regeneration: disabled. Use --watch to enable.
[21:32:59] Finished 'jekyll-build' after 1.58 s
[21:32:59] Starting 'sass'...
[21:33:00] Starting 'javascript'...
[21:33:00] Starting 'copy'...
DEPRECATION WARNING: Passing a string to call() is deprecated and will be illegal
in Sass 4.0. Use call(get-function("shake")) instead.

DEPRECATION WARNING: Passing a string to call() is deprecated and will be illegal
in Sass 4.0. Use call(get-function("shake")) instead.

DEPRECATION WARNING: Passing a string to call() is deprecated and will be illegal
in Sass 4.0. Use call(get-function("spin")) instead.

DEPRECATION WARNING: Passing a string to call() is deprecated and will be illegal
in Sass 4.0. Use call(get-function("spin")) instead.

DEPRECATION WARNING: Passing a string to call() is deprecated and will be illegal
in Sass 4.0. Use call(get-function("wiggle")) instead.

DEPRECATION WARNING: Passing a string to call() is deprecated and will be illegal
in Sass 4.0. Use call(get-function("wiggle")) instead.

Browserslist: caniuse-lite is outdated. Please run next command `yarn upgrade`
[21:33:02] Finished 'copy' after 2.38 s
[21:33:02] Finished 'sass' after 3.1 s
[21:33:04] Finished 'javascript' after 4.87 s
[21:33:04] Finished 'build' after 7.03 s
[21:33:04] Starting 'browser-sync'...
[21:33:04] Finished 'browser-sync' after 25 ms
[21:33:04] Starting 'watch'...
[21:33:05] Finished 'watch' after 55 ms
[21:33:05] Finished 'default' after 7.12 s
[BS] Access URLs:
 -----------------------------------------------
       Local: http://127.0.0.1.xip.io:3000
    External: http://192.168.188.100.xip.io:3000
 -----------------------------------------------
          UI: http://localhost:3001
 UI External: http://192.168.188.100.xip.io:3001
 -----------------------------------------------
[BS] Serving files from: _site/

Where do I fix this?
I couldn't find anything in the main source files