Do you want to request a feature or report a bug?
Bug / feature ?

What is the current behavior?
yarn install --ignore-optional tries to install also optional dependencies of sub modules. The while install process fails if one of the optional module installation fails.

What is the expected behavior?
To skip the optional dependencies of sub modules or to continue on errors.

Please mention your node.js, yarn and operating system version.
Node 7.5.0, Yarn v0.19.1, Ubuntu 14.04