https://fedoraproject.org/wiki/Changes/Python_3_as_Default from my understanding "Change definition of default python interpreter to python3" is different then he result below when you have removed all python2 dependencies and packages
[root@master:~]$ which python
/usr/bin/which: no python in (/usr/local/bin:/usr/bin:/usr/sbin:/scripts)
[root@master:~]$ python3
python3 python3.5 python3.5m
[harry@srv-rhsoft:~]$ rpm -q --file /usr/bin/python
python-2.7.12-6.fc24.x86_64
[harry@srv-rhsoft:~]$ ls /usr/bin/python
lrwxrwxrwx 1 root root 7 2016-09-29 15:31 /usr/bin/python -> python2
[harry@srv-rhsoft:~]$ cat /etc/redhat-release
Generic release 24 (Generic)