I had a variant of the same issue (on Windows), where npm did't want to upgrade because of some dependency threw an error, even though I had deleted and reinstalled Node.

I dimply delete the followingfolders, and npm installed correctly.

• C:\Users<USERNAME>\AppData\Roaming\npm
• C:\Users<USERNAME>\AppData\Roaming\npm-cache
• C:\Users<USERNAME>\AppData\Local\npm-cache

Just be careful when messing around in the AppData folder!