title: Failed to lock directory when installing R package using devtools::install_github()
body: <p>When installing an R package from GitHub using <code>devtools::install_github()</code>, the following error was returned:</p>
  
  <pre><code>ERROR: failed to lock directory ‘/Library/Frameworks/R.framework/Versions/3.3/Resources/library’ for modifying
  Try removing ‘/Library/Frameworks/R.framework/Versions/3.3/Resources/library/00LOCK-jrosen48-prcr-4f6f783’
  </code></pre>
  
  <p>When I navigate using Terminal on Macintosh <code>OS 10.12</code> to that location, it is not available ( R.framework did not appear in the "Frameworks" directory). </p>
  
  <p>How can I try removing <code>‘/Library/Frameworks/R.framework/Versions/3.3/Resources/library/00LOCK-jrosen48-prcr-4f6f783’</code>? Or, is there another workaround for this?</p>