When upgrading Bootstrap to v4.0.0 release, the bundler and minifier doesn’t work properly due to CSS variable is commonly used:
About 26 errors will show up in the Error List with the following message:
Expected semicolon or closing curly-brace found '-'
The environment in my machine has the following setup:
Downgrading the package to 2.5.357 doesn't fix the problem in my environment though some people mentioned it can work.
This issue in BuildBundlerMinifier is caused by another issue in package NUglify:
This issue has not been fixed yet.
It is also raised in GitHub:
Before this issue is fixed, you can use any of the following approaches to get it work:
I will keep this post updated when the issue is fixed permanently.