Ansible 'lookup' function

gistfile1.txt

ansible_code: 
- name: Pushing Authorized Keys to remote server(s)
       action: authorized_key user={{ item }} key="{{ lookup('file', "{{ item }}/id_rsa.pub") }}"
       with_items:
          - '{{ admins }}'

output: 
fatal: [54.201.43.177] => /Users/ndobbs/src/hc1dev/ansible/roles/common/files/{{item}}/id_rsa.pub does not exist

- name: Pushing Authorized Keys to remote server(s)
  action: authorized_key user={{ item }} key="{{ lookup('file', "{{ item }}/id_rsa.pub") }}"
  with_items:
    - ${admins}