node_modules/clean-css/lib/optimizer/level-2/invalid-property-error.js

function InvalidPropertyError(message) {
  this.name = 'InvalidPropertyError';
  this.message = message;
  this.stack = (new Error()).stack;
}

InvalidPropertyError.prototype = Object.create(Error.prototype);
InvalidPropertyError.prototype.constructor = InvalidPropertyError;

module.exports = InvalidPropertyError;