Yarn: Yarn, Travis-CI e Node 0.12.0: SyntaxError: Uso de const no modo estrito.

Quero usar o Yarn com Travis-CI, mas estou recebendo um erro com Node 0.12.0 :

/usr/share/yarn/lib-legacy/constants.js:7
const userHome = require('user-home');
^^^^^
SyntaxError: Use of const in strict mode.
    at exports.runInThisContext (vm.js:73:16)
    at Module._compile (module.js:443:25)
    at Object.Module._extensions..js (module.js:478:10)
    at Module.load (module.js:355:32)
    at Function.Module._load (module.js:310:12)
    at Module.require (module.js:365:17)
    at require (module.js:384:17)
    at Object.<anonymous> (/usr/share/yarn/bin/yarn.js:9:17)
    at Module._compile (module.js:460:26)
    at Object.Module._extensions..js (module.js:478:10)

Configuração do Travis-CI:

sudo: true
language: node_js

node_js:
  - "0.12"
  - iojs
  - "4"
  - "6"
  - "stable"

before_install:
  # https://yarnpkg.com/en/docs/install_ci
  - curl -sL https://deb.nodesource.com/setup_6.x | sudo -E bash -
  - sudo apt-key adv --keyserver pgp.mit.edu --recv D101F7899D41F3C3
  - echo "deb http://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
  - sudo apt-get update -qq
  - sudo apt-get install -y -qq yarn
cache:
  directories:
  - $HOME/.yarn-cache

install: "yarn"

script: "yarn run travis"

after_success:
  - yarn run test:coveralls
  - rm -rf ./coverage

Log Travis-CI:
https://travis-ci.org/sanex3339/javascript-obfuscator/jobs/169163143