Upgrade pyyaml to v3.12.
Upgrade pyyaml to v3.12.

nzlosh/st2,nzlosh/st2,StackStorm/st2,nzlosh/st2,StackStorm/st2,tonybaloney/st2,StackStorm/st2,nzlosh/st2,Plexxi/st2,Plexxi/st2,tonybaloney/st2,Plexxi/st2,Plexxi/st2,StackStorm/st2,tonybaloney/st2