frontools should fail, when there was a problem (error code != 0)

[amenk]

self@self-laptop:~/example/workspace/shop.example.com/tools$ gulp styles
[09:46:42] Using gulpfile ~/example/workspace/shop.example.com/vendor/snowdog/frontools/gulpfile.js
[09:46:42] Starting 'styles'...
[09:46:42] Starting 'inheritance'...
[09:46:44] Finished 'inheritance' after 1.76 s
Error in plugin 'sass'
Message:
    ../../../var/view_preprocessed/frontools/frontend/Example/default/styles/_variables.custom.scss
Error: Invalid CSS after "müll": expected "{", was ""
	on line 19 of ../../../var/view_preprocessed/frontools/frontend/Example/default/styles/_variables.custom.scss
>> müll
   -----^

[09:46:44] gulp-notify: [Error running Gulp] Error: ../../../var/view_preprocessed/frontools/frontend/Example/default/styles/_variables.custom.scss
Error: Invalid CSS after "müll": expected "{", was ""
	on line 19 of ../../../var/view_preprocessed/frontools/frontend/Example/default/styles/_variables.custom.scss
>> müll
   -----^

[09:46:44] Theme: Example print.css Compiled!
[09:46:45] Theme: blank print.css Compiled!
[09:46:45] Theme: blank styles.css Compiled!
[09:46:45] Finished 'styles' after 3.55 s
self@self-laptop:~/example/workspace/shop.example.com/tools$ echo $?
0

[amenk]

Approach: ivogabe/gulp-typescript#295 but no clue how to put this into frontools

[amenk]

https://stackoverflow.com/questions/45006766/exit-with-error-after-a-task-loaded-by-gulp-tasks-failed

[Igloczek]

Use --ci flag.