It would be helpful if user would get one-time dialog that he can check off with "OK" button informing he that it cannot reach the tumblerd dbus service, and he needs to install tumblerd to overcome the issue. priting in terminal (strerr/out) is not enough, since most people run this from menu. and even then, not everyone knows "org.freedesktop.thumbnails.Thumbnailer1" is actually tumblerd. this would be serve as an alternative to distro packagers simply forcing the tumblerd on every system... and propably we can then avoid few useless bug reports for "unworking thumbnails"
Note that a better wording might be “tumbler or a thumbnailing daemon”, since at one point other people might provide that interface.
It is implemented in master, I am having doubts wether or not I should add a checkbox 'do not show this message again' that triggers if the dialog is shown on next startup again or not.
The dialog is added, translatable and equiped with a 'do not show this message again' checkbox.