error cannot find module 'umask'

update your npm

$ npm install npm -g

I would try to update/install NPM

$ npm update -g npm

I know the answer!

Uninstall nodejs.

Delete all references to npm and nodejs (Program Files, Program Files(x86). Then also delete those in AppData/Roaming (npm and npm-cache to be sure).

Reinstall nodejs.

It works!