I've ran across bug 711399, and the following might be the case for you, too:
It looks that you had libcanberra-gtk-module installed, but then removed it (but not purged it).
This way the file /etc/X11/Xsession.d/52libcanberra-gtk-module_add-to-gtk-modules has been left, which adds canberra-gtk-module to GTK_MODULES.
You can fix the (rather cosmetic) error by e.g. pruning the package: "sudo dpkg -P libcanberra-gtk-module".
The real fix might be to only adjust GTK_MODULES, if the module itself (.so file) is still installed.
I've ran across bug 711399, and the following might be the case for you, too:
It looks that you had libcanberra- gtk-module installed, but then removed it (but not purged it).
This way the file /etc/X11/ Xsession. d/52libcanberra -gtk-module_ add-to- gtk-modules has been left, which adds canberra-gtk-module to GTK_MODULES.
You can fix the (rather cosmetic) error by e.g. pruning the package: "sudo dpkg -P libcanberra- gtk-module" .
The real fix might be to only adjust GTK_MODULES, if the module itself (.so file) is still installed.