message: Fix syntax to check if an element is in a set
diff: @@ -34,7 +34,7 @@ class WebpackPluginFailBuildOnWarning {
  if (warnings.length > 0) {
  // Throw error if there are unexpected warnings.
  for (let warning of warnings) {
  - if (!(warning.name in this.warningsWhitelist)) {
  + if (!this.warningsWhitelist.has(warning.name)) {
  process.on('beforeExit', () => {
  console.log(
  `You have some unexpected warning(s) in your webpack build. Exiting process as error.`,
  