Comment 1 for bug 1769107

The cause of this problem is that tripleo-upgrade was started in stable/pike branch, therefore there is not a stable/ocata branch for it. Therefor, Zuul imports master's branch of the role, which includes the following task:

- name: generate inventory file
  shell: |
    source {{ undercloud_rc }} ;
    tripleo-ansible-inventory --plan {{ overcloud_stack_name }} --static-yaml-inventory /tmp/fake-oc-hosts.yaml ;
    awk -F':' '/role_name/ {gsub("[[:space:][:punct:]]", "", $2); print $2}' /tmp/fake-oc-hosts.yaml
register: oc_roles

The tripleo-ansible-inventory command doesn't have a --static-yaml-inventory option in ocata, it was added for queens. Therefore, the task fails, as well as the whole job.