Multithreading not working under Ubuntu

[ghost]

I installed with pip as per instructions (under Ubuntu 16).

$ python setup.py test
running test
running egg_info
writing requirements to lightfm.egg-info/requires.txt
writing lightfm.egg-info/PKG-INFO
writing top-level names to lightfm.egg-info/top_level.txt
writing dependency_links to lightfm.egg-info/dependency_links.txt
reading manifest file 'lightfm.egg-info/SOURCES.txt'
writing manifest file 'lightfm.egg-info/SOURCES.txt'
running build_ext
copying build/lib.linux-x86_64-2.7/lightfm/_lightfm_fast_openmp.so -> lightfm
==================================================================================================================== test session starts ====================================================================================================================
platform linux2 -- Python 2.7.12, pytest-2.8.7, py-1.4.31, pluggy-0.3.1
collected 49 items 

tests/test_api.py ...........
tests/test_datasets.py ..
tests/test_evaluation.py ...
tests/test_fast_functions.py .
tests/test_movielens.py ................................

================================================================================================================ 49 passed in 114.88 seco

I'm seeing one python job using 100% of the CPU when there should be 20 threads running.