title: catching exception from boost::filesystem::is_directory
body: <p>I am currently catching errors from boost::filesystem::is_directory and showing the error to the user by calling "what()" on the exception.  This gives the reason for failure but the error is strange to the user.  For example:</p>
  
  <blockquote>
    <p>boost::filesystem::is_directory: Access is denied</p>
  </blockquote>
  
  <p>How can I catch the boost error and figure out what the actual cause is, so I can show a nicer error message?</p>