strings used as keys for hdf5 data structures must be set to byte string (e.g. b'V0') rather than plain strings
division no longer produced integers. I have seen several places where this breaks things (e.g. when indices are no longer integers) but there may also be places where it is quietly causing errors.
the where argument to plt.fill_between() requires explicit boolean typing
given that python2 is deprecated we need to move to python 3, which is breaking some of the code in the older notebooks.