This problem can have multiple solutions somne of them are here:
1:
Set ansible_python_interpreter: /usr/bin/python3 variable for all hosts that have python3 installed by default
OR
2: you can unisntall the ansible and try to install ansible using pip installer
$ pip3 install ansible
then when you check it will prompt
$ ansible --version | grep "python version"
python version = 3.6.2 (default, Sep 22 2017, 08:28:09) [GCC 7.2.1 20170915 (Red Hat 7.2.1-2)]