Author of PaPy here.
Thanks for giving PaPy a try. Although PaPy [https://github.com/mcieslik-mctp/papy] has never gained traction :(, I have been using it daily for over 5 years (no bugs in the scheduler so far). By now our PaPy based genomics pipelines have probably processed petabytes of data.
Cool, looks similarish; feel free to jump on freenode (usually during weekdays) and ping me, channel #openstack-state-management or #openstack-oslo
Pretty diagram also @ https://wiki.openstack.org/wiki/TaskFlow#Big_picture ;)
https://code.google.com/p/papy/
Will have to have a closer look at this one as well, though.