See
https://fedoramagazine.org/converting-networkmanager-from-ifcfg-to-keyfiles/
for more details on NetworkManager keyfiles.

Only MAC addresses and interface names are migrated for now.

TODO: migrate also IP addresses and routes.

Otherwise patching fails on files with spaces in them, often used by
NetworkManager:

Failed to rewrite MAC addresses and network interfaces in /mnt/local/etc/NetworkManager/system-connections/ZSSK
Failed to rewrite MAC addresses and network interfaces in WIFI.nmconnection

(the original file is named 'ZSSK WIFI.nmconnection').

It is our common practice to log and show messages with single-quoted
file names like "Processed the file 'file name'" and it is
especially useful with file names containing spaces.

Instead of chjecking whether the first member of the array is empty,
check whether the array is actually empty.