I am running Visual Studio 2017 and use the Task Runner to run tasks in my gulpfile. I recently updated a gulp task to ES6 and now am getting this error:
Issue solved by un-checking the box for the Node.js binary used by Task Runner:
In the menu, go to Tools > Options > Projects and Solutions > Web Package Management > External Web Tools and DESELECT the option for $(VSINSTALLDIR)\Web\External
The version installed in that directory doesn't support ES6 apparently.
References for solution here and here.