Easier reproducer in a built ubiquity tree:
$ GI_TYPELIB_PATH=src/webcam PYTHONPATH=. python -c 'from gi.repository import Gtk; import ubiquity.gtkwidgets; b=Gtk.Builder(); b.add_from_file("gui/gtk/stepPrepare.ui")'
Easier reproducer in a built ubiquity tree:
$ GI_TYPELIB_ PATH=src/ webcam PYTHONPATH=. python -c 'from gi.repository import Gtk; import ubiquity. gtkwidgets; b=Gtk.Builder(); b.add_from_ file("gui/ gtk/stepPrepare .ui")'