custom-file selector isn't a valid CSS value since upgrade to beta3

Created by: javinto

I have a Ruby-on-rails project (using the Bootstrap gem) where I use the custom file selector text according to the documentation:

$custom-file-text: (
  placeholder: (
    en: "Choose file...",
    nl: "Selecteer bestand..."
  ),
  button-label: (
    en: "Browse",
    nl: "Selecteer"
  )
);

After upgrading from beta 2.1 to beta 3 I now get the following error:

(en: "Choose file...", nl: "Selecteer bestand...") isn't a valid CSS value.

As I'm using SASS I ensured not upgrading any other gem but Bootstrap to exclude other gems from being the problem gem.

I could not find any upgrade or migration information on this specific component. So I suspect it is a bug. Here is my error: