Type in the terminal:
sudo gnome-tweak-tool
show
Traceback (most recent call last):
File "/usr/bin/gnome-tweak-tool", line 23, in <module>
import gi
ModuleNotFoundError: No module named 'gi'
The default python of centos7 is python3, and some old programs use python2
Guess this is causing the problem to be the first line in /usr/bin/gnome-tweak-tool
#!/usr/bin/env python
change to
#!/usr/bin/env python2