Comment 3 for bug 1467969

Hi, Lingxian!

What I do.
1. Installed devstack stable/kilo with mistral according this document https://github.com/openstack/mistral/blob/master/contrib/devstack/README.rst
2. Created very simple workflow with command `mistral workflow-create get_first_keystone_project.yaml`
3. Created cron trigger with command `mistral cron-trigger-create --pattern "* * * * *" test003 get_first_keystone_project input.json `
4. Wait few minutes.

What i've got.
Every in mistral's log there was en error https://bpaste.net/show/fa6f9049da77

Attached patch should solve the problem.

Thanks!