Note that this environment variable is read by GTK+ 2.x too, which may not have the same set of modules available for loading. Use GTK3_MODULES for modules that are only compatible with GTK+ 3.
and this module is only compatible with GTK 3, so we should be using GTK3_MODULES.
This typically produces some benign warnings in the outputs like:
Gtk-WARNING **: 13:33:12.201: GTK+ module /run/current-system/sw/lib/gtk-3.0/modules/libpantheon-filechooser-module.so cannot be loaded.
GTK+ 2.x symbols detected. Using GTK+ 2.x and GTK+ 3 in the same process is not supported.
Gtk-Message: 13:33:12.202: Failed to load module "pantheon-filechooser-module"
The docs on GTK_MODULES states this
and this module is only compatible with GTK 3, so we should be using
GTK3_MODULES.This typically produces some benign warnings in the outputs like: Gtk-WARNING **: 13:33:12.201: GTK+ module /run/current-system/sw/lib/gtk-3.0/modules/libpantheon-filechooser-module.so cannot be loaded. GTK+ 2.x symbols detected. Using GTK+ 2.x and GTK+ 3 in the same process is not supported. Gtk-Message: 13:33:12.202: Failed to load module "pantheon-filechooser-module"
We also use safer parameter expansions, see https://wiki-dev.bash-hackers.org/syntax/pe#use_an_alternate_value and https://wiki-dev.bash-hackers.org/syntax/pe#use_a_default_value.