npm install E401 npm authentication failed

[mcqueene]

I've never had a sample library tell me that I needed to authenticate. Since I don't see any other reports of this I assume I'm doing something silly but here's the error message I get when I tried to do an npm install after just unzipping the code to a folder on my laptop that was outside of github.

npm ERR! code E401 npm ERR! Unable to authenticate, your authentication token seems to be invalid. npm ERR! To correct this please trying logging in again with: npm ERR! npm login