np.load() fails to read empty archive created by np.savez()

Try this:

    np.savez('nothing.npz') # OK
    np.load('nothing.npz') # error

Loading fails:

    OSError: Failed to interpret file 'nothing.npz' as a pickle

It should succeed (and give you an object with no arrays inside).  Likewise for `savez_compressed()` (which also currently fails).

I'm using NumPy 1.13.1.