I have reproduced this error using karma-remap-istanbul and karma-coverage to show the source maps of my Webpack compiled build.

The error is talkative, it tells that the script can’t create a folder in `/` system root folder. Of course it’s supposed to create those report folders starting from a relative path. To enable it you should add the following option in your webpack.config.js file under the group output.

devtoolModuleFilenameTemplate: '[resource-path]'

Example here

This way we change the naming policy of the source-maps ad we won’t encounter permissions errors.

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