ProxyChanger Yum module tries to write proxy configuration in the files /etc/yum.conf or /etc/dnf/dnf.conf. So, to be able to update the contents of these files, the current user has to have write permissions. There are multiple ways to do this, depending, for example, if the computer is used by multiple users or not, so permissions can be given to a single user or a group.

To keep things simple, we can run this commands to allow the current user to write that file:

[ -e /etc/yum.conf ] && sudo chown ${USER} /etc/yum.conf
[ -e /etc/yum.conf ] && sudo chmod u+rw /etc/yum.conf

[ -e /etc/dnf/dnf.conf ] && sudo chown ${USER} /etc/dnf/dnf.conf
[ -e /etc/dnf/dnf.conf ] && sudo chmod u+rw /etc/dnf/dnf.conf