npm install failing (code : enoent)

I'm trying to install sharetribe on my aws server as said in the github repository but I get stuck when I have to install the Node modules (the third step). npm install gives me that log :

ubuntu@ip-*********:~/sharetribe$ npm install

> undefined postinstall /home/ubuntu/sharetribe
> cd client && npm install

npm WARN checkPermissions Missing write access to /home/ubuntu/sharetribe/client/customloaders/customfileloader/node_modules/big.js
npm WARN checkPermissions Missing write access to /home/ubuntu/sharetribe/client/customloaders/customfileloader/node_modules/json5
npm WARN checkPermissions Missing write access to /home/ubuntu/sharetribe/client/customloaders/customfileloader/node_modules/loader-utils
npm WARN checkPermissions Missing write access to /home/ubuntu/sharetribe/client/customloaders/customfileloader/node_modules
npm ERR! path /home/ubuntu/sharetribe/client/customloaders/customfileloader/node_modules/big.js
npm ERR! code ENOENT
npm ERR! errno -2
npm ERR! syscall access
npm ERR! enoent ENOENT: no such file or directory, access '/home/ubuntu/sharetribe/client/customloaders/customfileloader/node_modules/big.js'
npm ERR! enoent This is related to npm not being able to find a file.
npm ERR! enoent

npm ERR! A complete log of this run can be found in:
npm ERR!     /home/ubuntu/.npm/_logs/2017-06-12T09_54_44_274Z-debug.log
npm ERR! code ELIFECYCLE
npm ERR! errno 254
npm ERR! undefined postinstall: `cd client && npm install`
npm ERR! Exit status 254
npm ERR!
npm ERR! Failed at the undefined postinstall script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /home/ubuntu/.npm/_logs/2017-06-12T09_54_44_297Z-debug.log

It also appears that the node_modules folder doesn't exist (sharetribe/client/customloaders/customfileloader/node_modules/)

If anyone knows how to solve this enoent problem thanks in advance !

via JackA