In VS 2017 RC, go to Tools --> Options --> Projects and Solutions --> Web Package Management --> Package Restore. Notice that the casing of "NPM" is displayed as all uppercase. It should be all lowercase, to make it consistent with how it's displayed in the "npm Configuration File" item template and in the "Dependencies/npm" node of Solution Explorer.
In VS 2017 RC, go to Tools --> Options --> Projects and Solutions --> Web Package Management --> Package Restore. Notice that the casing of "NPM" is displayed as all uppercase. It should be all lowercase, to make it consistent with how it's displayed in the "npm Configuration File" item template and in the "Dependencies/npm" node of Solution Explorer.