Broken @import declaration of while importing .css file

[esperancaJS]

Running "cssmin:generated" (cssmin) task
Warning: Broken @import declaration of "../bower_components/bootstrap-datepicker/dist/css/bootstrap-datepicker.css",Broken @import declaration of "../bower_components/ngGallery/src/css/ngGallery.css"

versions

grunt-contrib-cssmin v: 0.14.0
Compass v: 1.0.3 (Polaris)
Sass v: 3.4.21 (Selective Steve)

I have tried uninstalling, npm cache clean and reinstaling grunt-contrib-cssmin but no dice.

[hitchmough]

@esperancaJS I've spotted something similar but with Google Fonts when there's a semi-colon in a rule i.e.
@import url('https://fonts.googleapis.com/css2?family=Open+Sans:ital,wght@0,400;0,700;0,800');
Will cause an error in CSSMin (that even --force) won't let it get past.