intltool-update runs during make check and finds files inside app:

    The following files contain translations and are currently not in use. Please
    consider adding these to the POTFILES.in file, located in the po/ directory.

    app/files/share/d-feet/ui/addconnectiondialog.ui
    app/files/share/d-feet/ui/app-menu.ui
    app/files/share/d-feet/ui/executedialog.ui
    app/files/share/d-feet/ui/introspection.ui
    app/files/share/d-feet/ui/mainwindow.ui