title: how to set default locale in R using mac os sierra
body: <p>I'm trying to install neuralnet package in R but gets the following error
  tar:failed to set default locale</p>
  
  <p>I have tried using <code>system("defaults write org.R-project.R force.LANG en_US.UTF-8")</code></p>
  
  <p>I have restarted R but same error</p>