test_extract_xi failing for MB_PYTHON_VERSION=3.6 PLAT=i686 and MB_PYTHON_VERSION=3.7 PLAT=i686

https://travis-ci.org/MacPython/scikit-learn-wheels/jobs/525429182
https://travis-ci.org/MacPython/scikit-learn-wheels/jobs/525429184