Merge branch 'release/0.81.8' into develop
Switch to my own version of django-shell-ipynb, to pass it any option, notably the one to listen on '*' IPs.
Avoid a loadful of post_create tasks on migrated articles that are already OK.
Simplify a lot the workers configuration, switch to gevent, make the pools bigger.
version bump for 0.81.9.
Merge branch 'release/0.81.9'