It looks like the solution to this is the package python3-gobject-cairo. The Snippets plugin works find on openSUSE 13.2 but if the python3-gobject-cairo is removed, then gedit crashes when a tab is closed.

Sadly python3-gobject-cairo isn't in SLED 12 or the SLE 12 SDK, I can't find a version of it built for SLED 12 and none of the openSUSE versions will install due to requiring differing versions of python than are in SLED 12. I can't get the python3-gobject-3.10.2-4.1.src.rpm for openSUSE 13.1 to build, although the source builds fine so long as make is called without DESTDIR.

A horrible, horrible, hack fix:

Install the packages glib2-devel libtool python3-devel python3-gobject-devel gobject-introspection gobject-introspection-devel python3-cairo-devel (you'll need the SDK enabled, which you can do in SUSE Customer Centre if you haven't already).

$ wget
$ tar xvf pygobject-3.10.2.tar.xz
$ cd pygobject-3.10.2
$ ./configure && make
Then as root
$ cd /usr/lib64/python3.4/site-packages/gi
$ cp /path/to/pygobject-3.10.2/gi/.libs/ . is the only file in the openSUSE 13.2 python3-gobject-cairo package.