This is copied verbatim from NixOS, which is under MIT licence.
https://github.com/NixOS/nixpkgs/blob/master/pkgs/desktops/gnome/misc/gpaste/
--- a/src/gnome-shell/extension.js
+++ b/src/gnome-shell/extension.js
@@ -6,6 +6,8 @@
 
 const Config = imports.misc.config;
 
+imports.gi.GIRepository.Repository.prepend_search_path('@typelibPath@');
+
 imports.gi.versions.Clutter = Config.LIBMUTTER_API_VERSION;
 imports.gi.versions.GLib = '2.0';
 imports.gi.versions.GPaste = '1.0';
--- a/src/gnome-shell/prefs.js
+++ b/src/gnome-shell/prefs.js
@@ -6,6 +6,8 @@
 
 const Gettext = imports.gettext;
 
+imports.gi.GIRepository.Repository.prepend_search_path('@typelibPath@');
+
 //const { GPaste } = imports.gi;
 
 const ExtensionUtils = imports.misc.extensionUtils;
--- a/src/libgpaste/settings/gpaste-settings.c
+++ b/src/libgpaste/settings/gpaste-settings.c
@@ -1013,7 +1013,11 @@
     }
     else
     {
-        return g_settings_new (G_PASTE_SETTINGS_NAME);
+        // library used by introspection requires schemas but we cannot set XDG_DATA_DIRS for the library
+        GSettingsSchemaSource *schema_source = g_settings_schema_source_new_from_directory ("@gschemasCompiled@", NULL, FALSE, NULL);
+        g_autoptr (GSettingsSchema) schema = g_settings_schema_source_lookup (schema_source, G_PASTE_SETTINGS_NAME, FALSE);
+        g_settings_schema_source_unref (schema_source);
+        return g_settings_new_full (schema, NULL, NULL);
     }
 }