$ python3 src/pomodouroboros/linux/gtk_progress_bar.py

(python3:868136): Gtk-CRITICAL **: 14:51:17.075: gtk_icon_theme_get_for_display: assertion 'GDK_IS_DISPLAY (display)' failed

(python3:868136): Gtk-CRITICAL **: 14:51:17.075: gtk_icon_theme_add_resource_path: assertion 'GTK_IS_ICON_THEME (self)' failed
Traceback (most recent call last):
  File "/home/jgerity/repos/Pomodouroboros.git/src/pomodouroboros/linux/gtk_progress_bar.py", line 115, in on_activate
    Gtk.StyleContext.add_provider_for_display(
TypeError: Argument 0 does not allow None as a value