What is going on here?!

ansible-playbook-output.txt

PLAY [gluster-nfs-server] *****************************************************

GATHERING FACTS ***************************************************************
ok: [srv1.domain.edu]
ok: [srv2.domain.edu]
ok: [srv3.domain.edu]
ok: [srv4.domain.edu]

TASK: [debug] *****************************************************************
ok: [srv1.domain.edu] => {
    "nfs_exports": "[{'hosts': ['host1.domain.edu(rw,fsid=0,anonuid=5001,anongid=5001)', 'host2.domain.edu(rw,fsid=0,anonuid=5001,anongid=5001)'], 'user': 'client1', 'dir': '/mnt/gluster/durable/clients/client1'}, {'hosts': ['host3.domain.edu(rw,fsid=0,anonuid=93824,anongid=93824)'], 'user': 'client2', 'dir': '/mnt/gluster/durable/clients/client2'}]"
}
ok: [srv4.domain.edu] => {
    "nfs_exports": "[{'hosts': ['host1.domain.edu(rw,fsid=0,anonuid=5001,anongid=5001)', 'host2.domain.edu(rw,fsid=0,anonuid=5001,anongid=5001)'], 'user': 'client1', 'dir': '/mnt/gluster/durable/clients/client1'}, {'hosts': ['host3.domain.edu(rw,fsid=0,anonuid=93824,anongid=93824)'], 'user': 'client2', 'dir': '/mnt/gluster/durable/clients/client2'}]"
}
ok: [srv2.domain.edu] => {
    "nfs_exports": "[{'hosts': ['host1.domain.edu(rw,fsid=0,anonuid=5001,anongid=5001)', 'host2.domain.edu(rw,fsid=0,anonuid=5001,anongid=5001)'], 'user': 'client1', 'dir': '/mnt/gluster/durable/clients/client1'}, {'hosts': ['host3.domain.edu(rw,fsid=0,anonuid=93824,anongid=93824)'], 'user': 'client2', 'dir': '/mnt/gluster/durable/clients/client2'}]"
}
ok: [srv3.domain.edu] => {
    "nfs_exports": "[{'hosts': ['host1.domain.edu(rw,fsid=0,anonuid=5001,anongid=5001)', 'host2.domain.edu(rw,fsid=0,anonuid=5001,anongid=5001)'], 'user': 'client1', 'dir': '/mnt/gluster/durable/clients/client1'}, {'hosts': ['host3.domain.edu(rw,fsid=0,anonuid=93824,anongid=93824)'], 'user': 'client2', 'dir': '/mnt/gluster/durable/clients/client2'}]"
}

TASK: [ensure that the export directories exist (only necessary on the master)] ***
fatal: [srv2.domain.edu] => with_items expects a list
fatal: [srv1.domain.edu] => with_items expects a list
fatal: [srv3.domain.edu] => with_items expects a list
fatal: [srv4.domain.edu] => with_items expects a list

FATAL: all hosts have already failed -- aborting

playlist.yml

---
- hosts: gluster-nfs-server
  sudo: yes
  tasks: 
    # --SNIP--
    - name: debug
      debug: var=nfs_exports

    - name: ensure that the export directories exist (only necessary on the master)
      file: path={{item.dir}} state=directory owner={{item.user}} group={{item.user}} mode=0750
      with_items: nfs_exports
      # NOTE: if I copy/paste the nfs_exports YAML here, it works. 
      # Also, the var works fine in a jinja template for-loop.

vars.yml

---
nfs_exports:
  - dir: /mnt/gluster/clients/client1
    user: client1
    hosts: 
      - host1.domain.edu(rw,fsid=0,anonuid=5001,anongid=5001)
      - host2.domain.edu(rw,fsid=0,anonuid=5001,anongid=5001)
  - dir: /mnt/gluster/clients/client2
    user: client2
    hosts: 
      - host3.domain.edu(rw,fsid=0,anonuid=93824,anongid=93824)