>>> data421 = load('de421.bsp')  # this worked
>>> data431 = load('de431.bsp')  # few seconds delay, and then:
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/yournamehere/anaconda2/anaconda/envs/myenv/lib/python2.7/site-packages/skyfield/iokit.py", line 43, in load
    download(url, path, verbose=verbose)
  File "/Users/yournamehere/anaconda2/anaconda/envs/myenv/lib/python2.7/site-packages/skyfield/iokit.py", line 74, in download
    raise IOError('cannot get {1} because {2}'.format(url, e))
IndexError: tuple index out of range