code editor plot preview throws unhandled exception if folder is not readable
A folder has only the permission “x”. A file within this folder has
permission “r”. Then one can open the file in the code editor (and also
execute it) but is not able to view the content of the folder.
However, the code editor throws an exception because the plot preview can not get the file content of the folder.
(from redmine: issue id 2416, created on 2016-07-08 by Christian.Glaser)