EspruinoHub installation fails on Raspberry Pi 3

Hi, I'm trying to get EspruinoHub to work on my RPi.
I'm on Raspbian Stretch and all packages are up to date. No manually installed "special" versions of any kind.

I'm following the steps from here: https://github.com/espruino/EspruinoHub; I'm only interested in the EspruinoHub and Web IDE Part, no need for NODE-RED.

The Setup fails at the "npm install" part with the following errors:

pi@raspberrypi:~/espruino/EspruinoHub $ npm install
(node:16913) [DEP0022] DeprecationWarning: os.tmpDir() is deprecated. Use os.tmpdir() instead.
npm ERR! Error: Method Not Allowed
npm ERR!     at errorResponse (/usr/share/npm/lib/cache/add-named.js:2­60:10)
npm ERR!     at /usr/share/npm/lib/cache/add-named.js:20­3:12
npm ERR!     at saved (/usr/share/npm/node_modules/npm-registr­y-client/lib/get.js:167:7)
npm ERR!     at FSReqWrap.oncomplete (fs.js:135:15)
npm ERR! If you need help, you may report this *entire* log,
npm ERR! including the npm and node versions, at:
npm ERR!     <http://github.com/npm/npm/issues>

npm ERR! System Linux 4.19.42-v7+
npm ERR! command "/usr/bin/node" "/usr/bin/npm" "install"
npm ERR! cwd /home/pi/espruino/EspruinoHub
npm ERR! node -v v8.11.1
npm ERR! npm -v 1.4.21
npm ERR! code E405
npm ERR! 
npm ERR! Additional logging details can be found in:
npm ERR!     /home/pi/espruino/EspruinoHub/npm-debug.­log
npm ERR! not ok code 0
pi@raspberrypi:~/espruino/EspruinoHub $ 

I'm not really familiar with node.js and npm, and I suspect the environment setup is not correct. I installed node & npm from the defailt raspbian repos.

Any Ideas?