What causes the WARNING "Failure using method (v2_playbook_on_stats) in callback plugin" when launching the playbook?

Question

linux

Good afternoon.
I'm just starting to understand Ansible (according to the advice from the last question ) and I ran into the following problem.
We have: Ansible 2.1.2.0 installed on Ubuntu 16.04 from ppa:ansible/ansible.
File /etc/ansible/hosts:

[localhost]
localhost ansible_connection=local

ping.yml file

---
- name: Ping
  hosts: all
  tasks:
    - name: Test connection
      ping:

$ ansible-playbook ping.yml --verbose

Using /etc/ansible/ansible.cfg as config file

PLAY [Ping] ********************************************************************

TASK [setup] *******************************************************************
ok: [localhost]

TASK [Test connection] *********************************************************
ok: [localhost] => {"changed": false, "ping": "pong"}

PLAY RECAP *********************************************************************
 [WARNING]: Failure using method (v2_playbook_on_stats) in callback plugin 
(<ansible.plugins.callback.default.CallbackModule object
at 0x7f0c480bf510>): ''

1. A warning appears at the end of the execution of any other playbooks collected from Ansible Galaxy roles. That is, it does not look like a feature of running ping on localhost.
2. On the Internet, including in issues on the developers' GitHub, there are several problems with a similar error. As far as I can tell, all of them have been fixed, or upon closer examination, it becomes clear that this is not my case.
You are still on Ansible, so I'm not sure what it is worth writing to developers in issues, and for now I decided to ask here. I would be grateful for any advice.

Answer 1

do not make unnecessary ping and life will become better