Unable to set unity-gtk-module on the session using gsettings

[Lester Carballo Pérez]

Is impossible enable the unity-gtk-module using gsettings:
org.cinnamon.settings-daemon.plugins.xsettings enabled-gtk-modules

Tested on Cinnamon 2.2.16 over Ubuntu 15.04 on a virtualbox

Step to be reproduced:
1- gsettings set org.cinnamon.settings-daemon.plugins.xsettings enabled-gtk-modules "['unity-gtk-module']"
2- logout and try to login.

.xsession-errors:

openConnection: connect: No such file or directory
cannot connect to brltty at :0

(cinnamon-settings-daemon:1432): media-keys-plugin-WARNING **: Grab failed for some keys, another application may already have access the them.
pci id for fd 10: 80ee:beef, driver (null)
libGL error: core dri or dri2 extension not found
libGL error: failed to load driver: vboxvideo
Window manager warning: Software rendering detected: Gallium 0.4 on llvmpipe (LLVM 3.6, 128 bits)

** (polkit-gnome-authentication-agent-1:1518): WARNING **: Unable to register authentication agent: GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: An authentication agent already exists for the given subject
Cannot register authentication agent: GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: An authentication agent already exists for the given subject
cinnamon-session[1249]: WARNING: Application 'cinnamon.desktop' killed by signal 15
pci id for fd 10: 80ee:beef, driver (null)
libGL error: core dri or dri2 extension not found
libGL error: failed to load driver: vboxvideo
Window manager warning: Software rendering detected: Gallium 0.4 on llvmpipe (LLVM 3.6, 128 bits)
cinnamon-session[1249]: WARNING: App 'cinnamon.desktop' respawning too quickly
cinnamon-session[1249]: CRITICAL: We failed, but the fail whale is dead. Sorry....
Traceback (most recent call last):
  File "/usr/bin/cinnamon-launcher", line 34, in <module>
    os.execvp(FALLBACK_COMMAND, (FALLBACK_COMMAND,) + FALLBACK_ARGS)
  File "/usr/lib/python2.7/os.py", line 346, in execvp
    _execvpe(file, args)
  File "/usr/lib/python2.7/os.py", line 382, in _execvpe
    func(fullname, *argrest)
OSError: [Errno 2] No such file or directory
cinnamon-session[1249]: WARNING: Application 'cinnamon.desktop' killed by signal 11

Original report:
http://www.webupd8.org/2015/05/global-menu-applet-for-cinnamon-desktop.html

Thanks and regards.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.