I do not know why this is not documented well and why Ubuntu has decided not to update their repositories, but I have been encountering issues when installing Node.js packages.

npm ERR! Error: failed to fetch from registry: bower

Fortunately you can fix this by removing your current Node.js and npm installations and tapping in a custom Ubuntu repository for a newer build of Node.js.

sudo apt-get purge nodejs npm
sudo apt-get update
sudo apt-get install -y python-software-properties python g++ make
sudo add-apt-repository ppa:chris-lea/node.js
sudo apt-get update
sudo apt-get install nodejs

Node.js in the new repository is bundled with npm so it is not needed to install npm separately. In fact, you will probably get an error doing so.

After you have done those steps, try installing your package again and you should be good to go!