Comment # 1 on bug 952324 from Dominique Leuenberger

Let me post here as well the answer I gave on the mailing list, so it becomes
clear what needs to be done:

That one can be seen as a libzypp bug or a thunar bug; the fix is
certainly easier in Thunar.

The package provides:
  appdata(thunar.appdata.xml)
and
  application(Thunar.desktop)

Now, thunar does not really do anything 'invalid' there, as the
provided appdata.xml correctly references Thunar.desktop, but libzypp
falls on the nose with it.

For this error to disappear, the appdata file and the .desktop file
should use the same basename.

So the easiest fix is for Thunar to rename thunar.appdata.xml to
Thunar.appdata.xml; then the problem disappears (do not rename the
.desktop file, or you will need to patch the appdata.xml, which
references the .desktop file by name)

In the longer run, libzypp might need a fix to not be so pedantic about
it (the AppData standard does not mandate the names to be equal; but
from any upstream project PoV, it's good practice to reuse the naming
schemes throughout the project anyway).