[qgis-qwc2] installation error node themesConfig.js

[Steve.Toutant at inspq.qc.ca]

hi,
I'm trying to install qwc2 on ubuntu 16.04 and get the following error 
after yarn start

node themesConfig.js
/var/www/html/qwc2-demo-app/themesConfig.js:42
    let bboxw = extent[2] - extent[0];
    ^^^

SyntaxError: Block-scoped declarations (let, const, function, class) not 
yet supported outside strict mode
    at exports.runInThisContext (vm.js:53:16)
    at Module._compile (module.js:374:25)
    at Object.Module._extensions..js (module.js:417:10)
    at Module.load (module.js:344:32)
    at Function.Module._load (module.js:301:12)
    at Function.Module.runMain (module.js:442:10)
    at startup (node.js:136:18)
    at node.js:966:3

I know nothing about node and yarn, I just follow the recipe. Is there 
something I can do or it is a bug
thanks!

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