If you are doing a custom deployment and image, make sure that when you rsync'd or tar'd that you didn't mess up the symlnk of /etc/mtab to /proc/self/mounts
ln --force -s /proc/self/mounts /etc/mtab
Will fix this........
In this case I am executing using "python3" but what you find in cases like this can be surprising.
The most common issues are that someone has a module for python 2 "pip" and doesn't realize they need "pip3" to install it for python3, but this is not one of those cases.
ModuleNotFoundError: No module named 'bs4'
OKmaybe we didn't install it for python3?
Done on Centos 7.3 very important as clearly based on older guides it was a lot easier and more simpler! Hint do not use grub2-install!
If you have trouble booting after this check this CentOS mdadm RAID booting/fixing guide.
One huge caveat if you are an oldschool user or sysadmin who has avoided UEFIbooting