Comment 10 for bug 841463

The magnatune plugin is the culprit.

Here the trace I have when loading the magnatune plugin:
/usr/lib/python2.7/dist-packages/gobject/constants.py:24: Warning: g_boxed_type_register_static: assertion `g_type_from_name (name) == 0' failed
  import gobject._gobject
TypeError: metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases
**
ERROR:/build/buildd/pygobject-3.0.0/gi/_gobject/pygobject.c:929:pygobject_new_full: assertion failed: (tp != NULL)
Abandon

This is kind of critical, as rhythmbox refuses to start if magnatune is activated in the plugin panel.