ansible callback plugin that warns you of --check mode

check_mode_indicator.py

from __future__ import (absolute_import, division, print_function)
__metaclass__ = type

DOCUMENTATION = '''
    callback: check_mode_indicator
    type: aggregate
    short_description: shows a warning if you run ansible in check mode
    description:
        - This callback module shows a big WARNING when you run ansible in check mode.
'''

from ansible.plugins.callback import CallbackBase
from ansible import context


class CallbackModule(CallbackBase):
    """
    This callback module shows a big WARNING when you run ansible in check mode.
    """
    CALLBACK_VERSION = 2.0
    CALLBACK_TYPE = 'aggregate'
    CALLBACK_NAME = 'check_mode_indicator'
    CALLBACK_NEEDS_WHITELIST = False

    def __init__(self):
        super(CallbackModule, self).__init__()

    def v2_playbook_on_stats(self, stats):
        #print(context.CLIARGS)
        if context.CLIARGS['check']:
            self._display.warning("*** THIS WAS ONLY A CHECK MODE RUN ***")

you need to include its path into your .ansible.cfg like this:

[defaults]
callback_plugins = /usr/share/ansible_plugins/callback_plugins:~/ansible/callback_plugins