D18599: Use specific error message if file/folder name contains '/'

[Shubham]

shubham marked an inline comment as done.

REPOSITORY
  R241 KIO

REVISION DETAIL
  https://phabricator.kde.org/D18599

To: shubham, ngraham, #vdg, #frameworks, #dolphin
Cc: kde-frameworks-devel, michaelh, ngraham, bruns