When I am editing an existing file in a directory in which I do not have a file creation right everything is fine. I can save the modified file (with write access) without problems as expected.
Once I enable Back Up Before Saving1 in Atom settings then the file saving in such a case always fails with an error message like:
Unable to save file
Atom always tries to create the backup file in the same directory as the file about to be saved. Of course this fails when I do not have the right to create a new file there. I think it would be very useful if Atom creates the backup file in a temporary directory instead in such cases.
1 I want to have backups enabled because I want to minimize the risk of losing the content of my file during saving in various conditions.
2 I have shortened the backup file path in the error message.