ERRO Ansible! O objeto 'AnsibleUnicode' não possui atributos 'chaves

Question

Estou executando o Ansible pela primeira vez e recebo este erro:

root@raspberrypi:/opt/ansible# ansible-playbook -i /opt/ansible/hosts simple.yml 
ERROR! 'AnsibleUnicode' object has no attribute 'keys'
/opt/ansible/hosts:1: Expected key=value host variable assignment, got: juniper

Conteúdo de simple.yml:

---
- name: Verifying NETCONF
  hosts: juniper
  tasks: 
    - name: Verifying NETCONF
      wait_for: host={{ansible_ssh_host}} port=22

Conteúdo de hosts:

juniper ansible_connection=local juniper ansible_port=22 ansible_host=172.16.0.1 juniper_user=root juniper_passwd=Juniper.2015

Alguma sugestão?