Adapted from OpenBSD 
http://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/ports/devel/glib2/patches/patch-gio_gunixmount_c?rev=1.19&content-type=text/plain

to make unmount work for non-root users since our transition to Gnome 3

--- glib-2.82.0/gio/gunixmount.c.orig
+++ glib-2.82.0/gio/gunixmount.c
@@ -334,12 +334,9 @@
                       gpointer             user_data)
 {
   GUnixMount *unix_mount = G_UNIX_MOUNT (mount);
-  char *argv[] = {"umount", NULL, NULL};
+  char *argv[] = {"/usr/bin/pfexec", "/usr/bin/rmumount", NULL, NULL}; 
 
-  if (unix_mount->mount_path != NULL)
-    argv[1] = unix_mount->mount_path;
-  else
-    argv[1] = unix_mount->device_path;
+  argv[2] = unix_mount->device_path;
 
   eject_unmount_do (mount, cancellable, callback, user_data, argv, "[gio] unmount mount");
 }