OMP_NUM_THREADS issue on niagara

From Sigurd:

Have you had a problem where running nemo fails if OMP_NUM_THREADS is not set to 1? I just encountered this on niagara. Everything hangs forever during some astropy-related import, but doing that import in isolation works fine. Looking at strace, it seems to be a sort of threading deadlock.

I worked around it by setting OMP_NUM_THREADS=1