Comment 5 for bug 914140

I'm writing an app for Ubuntu App Showdown and I also used to get this. At least in my case it turned out I had some small python snippets (for testing various stuff) in a directory under the project that were the problem ( i.e. variety/snippets/) - after I removed them, all ran fine.
Here's with --verbose:

peter@plpc:~/dev/variety$ quickly package --verbose
/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
/usr/lib/python2.7/dist-packages/gtk-2.0/gtk/__init__.py:40: Warning: specified class size for type `PyGtkGenericCellRenderer' is smaller than the parent type's `GtkCellRenderer' class size
  from gtk import _gtk
/usr/lib/python2.7/dist-packages/gtk-2.0/gtk/__init__.py:40: Warning: g_type_get_qdata: assertion `node != NULL' failed
  from gtk import _gtk
setup.py install_egg_info failed
An error has occurred when creating debian packaging
ERROR: can't create or update ubuntu package
ERROR: package command failed
Aborting

I can attach the zipped project as it used to fail, if you request it.