gtk fault on startup macOS

[poesel]

Nelson:~ markus$ xpra attach ssh://pi@ra --opengl=no
/Applications/Xpra.app/Contents/Resources/lib/python/xpra/platform/darwin/gui.py:110: Warning: invalid cast from 'GtkMenuBar' to 'GtkWindow'
  osxapp.set_menu_bar(mh.rebuild())

(Xpra:66826): Gtk-CRITICAL **: 15:11:27.096: gtk_window_add_accel_group: assertion 'GTK_IS_WINDOW (window)' failed
2020-03-15 15:11:27,351 Xpra GTK3 client version 3.0.7-r25628 64-bit
2020-03-15 15:11:27,380  running on Mac OS X 10.15.3

I get this fault everytime I start xpra. However the program runs without problems.

[Antoine Martin]

Those messages are harmless warnings that are unavoidable with GTK on macos, I have added them to the wiki/FAQ