I have NVM 0.30.1 and used it to install node.js v5.4.0 (with NPM 3.5.4) on Fedora 22. When I run npm update -g, I receive the following warnings:
If people with linux are facing the problem, here is the solution:
As of the date of this post, the NPM version packaged with Nodejs doesn't work. If you installed this package, run
sudo rm -rf /usr/local/bin/npm
sudo apt-get install node
sudo mv /usr/bin/npm /usr/local/bin/npm
New version should be 3.10.8 and the old error gone