How resolve WARN when run ansible: [WARNING]: Skipping plugin as it seems to be invalid?

When I run ansible command, like this:

ansible -i host all -m ping

I got this warnings:

[WARNING]: Skipping plugin (/usr/lib/python2.7/dist-packages/ansible/plugins/callback/foreman.py) as it seems to be invalid: from_buffer() cannot return the address of the raw string
within a str or unicode or bytearray object
[WARNING]: Skipping plugin (/usr/lib/python2.7/dist-packages/ansible/plugins/callback/grafana_annotations.py) as it seems to be invalid: from_buffer() cannot return the address of the
raw string within a str or unicode or bytearray object
[WARNING]: Skipping plugin (/usr/lib/python2.7/dist-packages/ansible/plugins/callback/hipchat.py) as it seems to be invalid: from_buffer() cannot return the address of the raw string
within a str or unicode or bytearray object
[WARNING]: Skipping plugin (/usr/lib/python2.7/dist-packages/ansible/plugins/callback/nrdp.py) as it seems to be invalid: from_buffer() cannot return the address of the raw string
within a str or unicode or bytearray object
[WARNING]: Skipping plugin (/usr/lib/python2.7/dist-packages/ansible/plugins/callback/slack.py) as it seems to be invalid: from_buffer() cannot return the address of the raw string
within a str or unicode or bytearray object
[WARNING]: Skipping plugin (/usr/lib/python2.7/dist-packages/ansible/plugins/callback/splunk.py) as it seems to be invalid: from_buffer() cannot return the address of the raw string
within a str or unicode or bytearray object
[WARNING]: Skipping plugin (/usr/lib/python2.7/dist-packages/ansible/plugins/callback/sumologic.py) as it seems to be invalid: from_buffer() cannot return the address of the raw string
within a str or unicode or bytearray object

Why this happen, and how can I remove this warning?

Server params:
ansible version – 2.9
OS version – Ubuntu 16.04

ansible --version

python version = 2.x.x (…)