Can I prevent the use of threads at runtime?

[Ned Batchelder]

I'm using OpenBLAS via numpy with Python 2.7.  I run code in a limited environment (a sandbox for running student and instructor code on edX), so I try to limit the resources used.  On Ubuntu 12.04, I set RLIMIT_NPROC to 0, to prevent subprocesses.  But on Ubuntu 16.04, that limit also applies to threads.  When I run some sample code, it fails with this output:

                OpenBLAS blas_thread_init: pthread_create: Resource temporarily unavailable
                OpenBLAS blas_thread_init: RLIMIT_NPROC 0 current, 0 max
                Traceback (most recent call last):
                  File "jailed_code", line 15, in <module>
                    exec code in g_dict
                  File "<string>", line 3, in <module>
                  File "/edx/app/edxapp/venvs/edxapp-sandbox/local/lib/python2.7/site-packages/numpy/__init__.py", line 137, in <module>
                    import add_newdocs
                  File "/edx/app/edxapp/venvs/edxapp-sandbox/local/lib/python2.7/site-packages/numpy/add_newdocs.py", line 9, in <module>
                    from numpy.lib import add_newdoc
                  File "/edx/app/edxapp/venvs/edxapp-sandbox/local/lib/python2.7/site-packages/numpy/lib/__init__.py", line 4, in <module>
                    from type_check import *
                  File "/edx/app/edxapp/venvs/edxapp-sandbox/local/lib/python2.7/site-packages/numpy/lib/type_check.py", line 8, in <module>
                    import numpy.core.numeric as _nx
                  File "/edx/app/edxapp/venvs/edxapp-sandbox/local/lib/python2.7/site-packages/numpy/core/__init__.py", line 11, in <module>
                    from numeric import *
                  File "/edx/app/edxapp/venvs/edxapp-sandbox/local/lib/python2.7/site-packages/numpy/core/numeric.py", line 817, in <module>
                    from _dotblas import dot, vdot, inner, alterdot, restoredot
                KeyboardInterrupt
 
Is there some way that I can instruct OpenBLAS not to use any threads at all?  I've searched postings in this group, but I am confused about which options are build-time, and which are run-time.  I've tried a few of the environment variables (OPENBLAS_NUM_THREADS and OMP_NUM_THREADS), but they don't have any effect.  It isn't an option for me to build my own OpenBLAS.  Is there anything I can do?

Thanks,

--Ned.