Change system accounts not on the user provided ignore-list items are not JSON serializable

[krhubert]

Hi,

On some systems, I'm getting the error as below. For now I'm not seeing why this colud happen.

$ (ansible host) ansible --version
ansible 2.3.0.0
  python version = 3.5.2+ (default, Sep 22 2016, 12:18:14) [GCC 6.2.0 20160927]
$ (ansible host) lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 16.10
Release:	16.10
Codename:	yakkety
$ (provision host) lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 16.04.2 LTS
Release:	16.04
Codename:	xenial

TASK [os-hardening : remove always ignored system accounts from list] ***********************************************************************************************************************************************************************
task path: /root/ops/ansible/roles/os-hardening/tasks/user_accounts.yml:27
 [WARNING]: Failure using method (v2_runner_on_ok) in callback plugin (<ansible.plugins.callback.default.CallbackModule object at 0x7fe967f75898>): {'_apt', 'messagebus', 'dnsmasq', 'systemd-bus-proxy', 'systemd-timesync', 'mail',
'daemon', 'www-data', 'systemd-network', 'man', 'syslog', 'backup', 'uuidd', 'irc', 'proxy', 'systemd-resolve', 'ntp', 'uucp', 'lp', 'list', 'sys', 'gnats', 'pollinate', 'bin', 'news', 'lxd', 'games', 'sshd'} is not JSON serializable


TASK [os-hardening : change system accounts not on the user provided ignore-list] ***********************************************************************************************************************************************************
task path: /root/ops/ansible/roles/os-hardening/tasks/user_accounts.yml:32
The full traceback is:
Traceback (most recent call last):
  File "/usr/local/lib/python3.5/dist-packages/ansible/executor/task_executor.py", line 97, in run
    item_results = self._run_loop(items)
  File "/usr/local/lib/python3.5/dist-packages/ansible/executor/task_executor.py", line 290, in _run_loop
    res = self._execute(variables=task_vars)
  File "/usr/local/lib/python3.5/dist-packages/ansible/executor/task_executor.py", line 521, in _execute
    result = self._handler.run(task_vars=variables)
  File "/usr/local/lib/python3.5/dist-packages/ansible/plugins/action/normal.py", line 45, in run
    results = merge_hash(results, self._execute_module(tmp=tmp, task_vars=task_vars, wrap_async=wrap_async))
  File "/usr/local/lib/python3.5/dist-packages/ansible/plugins/action/__init__.py", line 635, in _execute_module
    (module_style, shebang, module_data, module_path) = self._configure_module(module_name=module_name, module_args=module_args, task_vars=task_vars)
  File "/usr/local/lib/python3.5/dist-packages/ansible/plugins/action/__init__.py", line 160, in _configure_module
    task_vars=task_vars, module_compression=self._play_context.module_compression)
  File "/usr/local/lib/python3.5/dist-packages/ansible/executor/module_common.py", line 796, in modify_module
    (b_module_data, module_style, shebang) = _find_module_utils(module_name, b_module_data, module_path, module_args, task_vars, module_compression)
  File "/usr/local/lib/python3.5/dist-packages/ansible/executor/module_common.py", line 629, in _find_module_utils
    python_repred_params = repr(json.dumps(params))
  File "/usr/lib/python3.5/json/__init__.py", line 230, in dumps
    return _default_encoder.encode(obj)
  File "/usr/lib/python3.5/json/encoder.py", line 198, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/usr/lib/python3.5/json/encoder.py", line 256, in iterencode
    return _iterencode(o, 0)
  File "/usr/lib/python3.5/json/encoder.py", line 179, in default
    raise TypeError(repr(o) + " is not JSON serializable")
TypeError: {'_apt', 'messagebus', 'dnsmasq', 'systemd-bus-proxy', 'systemd-timesync', 'mail', 'daemon', 'www-data', 'systemd-network', 'man', 'syslog', 'backup', 'uuidd', 'irc', 'proxy', 'systemd-resolve', 'ntp', 'uucp', 'lp', 'list', 'sys', 'gnats', 'pollinate', 'bin', 'news', 'lxd', 'games', 'sshd'} is not JSON serializable

fatal: [clap-instance-rh6g]: FAILED! => {
    "failed": true,
    "msg": "Unexpected failure during module execution.",
    "stdout": ""
}