OCI: Leapp Upgrade Fails with the Error "DNF execution failed with non zero exit code"

Applies To

Oracle Cloud Infrastructure - Version N/A and later

Linux OS - Version Oracle Linux 7.0 and later

Symptoms:

Leapp upgrade from Oracle Linux 7 to Oracle Linux 8 fails with the following error.

Risk Factor: high (error)

Title: DNF execution failed with non zero exit code.

Summary: {"hint": "If there was a problem reaching remote content (see stderr output) and proxy is configured in the YUM/DNF configuration file,
the proxy configuration is likely causing this error. Make sure the proxy is properly configured in /etc/dnf/dnf.conf. It's also possible the 
proxy settings in the DNF configuration file are incompatible with the target system. A compatible configuration can be placed in 
/etc/leapp/files/dnf.conf which, if present, it will be used during some parts of the upgrade instead of original /etc/dnf/dnf.conf. 
In such case the configuration will also be applied to the target system. Note that /etc/dnf/dnf.conf needs to be still