travis CI is failing for python 3.6

[lgarithm]

�[0K$ python tests/test_mnist_simple.py
RuntimeError: module compiled against API version 0xc but this version of numpy is 0xb
ImportError: numpy.core.multiarray failed to import
ImportError: numpy.core.umath failed to import
ImportError: numpy.core.umath failed to import
2018-01-28 07:25:15.979559: F tensorflow/python/lib/core/bfloat16.cc:664] Check failed: PyBfloat16_Type.tp_base != nullptr 
/home/travis/.travis/job_stages: line 57:  2492 Aborted                 (core dumped) python tests/test_mnist_simple.py

travis_time:end:13603272:start=1517124314833580397,finish=1517124316123755764,duration=1290175367
�[0K
�[31;1mThe command "python tests/test_mnist_simple.py" exited with 134.�[0m

Done. Your build exited with 1.

[jart]

Are you on TF 1.5? This might be a dupe of tensorflow/tensorflow#16488

[lgarithm]

We run pip install tensorflow in .travis.yml without specific version, so it should be TF 1.5 now.