This isn't as significant as it looks, as it's principally a big
dedent in zmq.ipkernel. All the single-method Kernel subclasses were just dedented, and are used as functions. This lets them be plugged into the existing kernel's event loop.
The enable_pylab and magic_gui methods in zmqshell only differ from the originals in the source of the enable_gui function, and the change of the default pylab backend to inline, from matplotlib autodetect.