- Upstream recommends spawn_async() instead of spawn_sync(), but the bindings
  for it are erroneous.

  See: https://gitlab.gnome.org/GNOME/vala/issues/721
       https://gitlab.gnome.org/GNOME/gobject-introspection/merge_requests/168
       https://gitlab.gnome.org/GNOME/vte/issues/227

- The upstream GTK devel branch has dropped some X11-specific APIs, including
  the interface for urgency hints. Eventually, this feature will have to be
  removed from weltschmerz too.

  See: https://gitlab.gnome.org/GNOME/gtk/merge_requests/766

- Upstream VTE indicates [1] [2] [3] that VteTerminal is incompatible with
  GtkScrolledWindow. weltschmerz has been using the latter since its launch,
  but has yet to run into any problem with it. Depending on how GTK/VTE will
  handle outstanding issues [4] [5], we might have to take action in the
  future. Bug reports or comments regarding this are appreciated.

  Note: A cursory check revealed that at least one other VTE-based emulator,
  terminator, seems to be using GtkScrolledWindow as well. According to [2], an
  implementation for gnome-terminal is planned too, but work seems to have
  stalled.

  [1] https://developer.gnome.org/vte/unstable/VteTerminal.html (see #Description)
  [2] https://gitlab.gnome.org/GNOME/vte/issues/11#note_264921
  [3] https://bugzilla.gnome.org/show_bug.cgi?id=733210#c2
  [4] https://gitlab.gnome.org/GNOME/vte/-/issues/183
  [5] https://gitlab.gnome.org/GNOME/vte/-/issues/234