Concurrency problem creating assets directory

In OpenStack Horizon we are seeing this error intermittently during automated testing:

File exists: '/opt/stack/new/horizon/static/scss/assets'
http://logs.openstack.org/81/120281/3/check/check-tempest-dsvm-neutron-full/fbe5341/logs/screen-horizon.txt.gz

It looks like the problem is in this line
https://github.com/fusionbox/django-pyscss/blob/master/django_pyscss/scss.py#L161

It would be great if that code didn't throw the File Exists error if the path was created successfully by another thread/process.