Error: Cannot find module 'postcss-loader' 

While deploying the plugin I get :

Error: Cannot find module 'postcss-loader'
Require stack: ......

any idea? I was able to successfully install and deploy the "old" version of the plugin some months ago, I wanted to do a new install today, and I got this error.
I also installed manually postcss, but the the deploy error still there.


Max