title: Ansible TypeError: must be string or buffer, not list
body: <p>Below task is failing with must be string or buffer, not list and when I use the same loop over shell and the output prints string, so not sure where it is going wrong. I have used <code>loop</code> also, it is also giving same output</p>
  
  <pre><code>- name: Provide Ambari cluster user role to users in file {{ cluster_user_group_file }}
    uri:
        url: "http://{{ ansible_fqdn }}:8080/api/v1/clusters/{{ cluster_name }}/privileges"
        method: POST
        force_basic_auth: yes
        user: "{{ ambari_admin_user }}"
        password: "{{ ambari_admin_password }}"
        headers: '{"X-Requested-By":"ambari"}'
        body: "[{\"PrivilegeInfo\":{\"permission_name\":\"CLUSTER.USER\",\"principal_name\":\"{{ item }}\",\"principal_type\":\"GROUP\"}}]"
        status_code: 200,201,202,409
        timeout: 60
        return_content: no
    with_items: "{{ lookup('file', '{{ cluster_user_group_file }}').split(',') }}"
  </code></pre>