Quantlib version 1.9.1
Traceback (most recent call last):
  File "cb.py", line 51, in <module>
    main()
  File "cb.py", line 48, in main
    print(discountTermStructure.discount(t_now))
  File "/usr/lib/python3.6/site-packages/QuantLib/QuantLib.py", line 5495, in discount
    return _QuantLib.YieldTermStructureHandle_discount(self, *args)
RuntimeError: 1st iteration: failed at 3rd alive instrument, pillar December 30th, 2016, maturity December 30th, 2016, reference date December 16th, 2016: root not bracketed: f[-1,1] -> [-2.119999e-03,-2.119999e-03]