Improve "insufficient disk space" error message
Summary: The prior error was misleading, and always said "Disk full." even when the disk wasn't actually full; not having enough space to move or copy the requested file doesn't mean that the disk is full! This patch re-words the error message to be clearer and still work when errorString is defined (as it always should be).
Reviewed By: shubham
Subscribers: broulik, abetts, kde-frameworks-devel
Differential Revision: https://phabricator.kde.org/D15557