1 - libudev: return errno or set errno
3 - delete mobile-action-modeswitch
4 (moved to usb_modeswitch)
6 - /run/udev/control socket
7 (add ConditionVirtualization=!pidns)
9 - kill rules_generator:
10 - no longer rename netifs in kernel namespace
11 - drop persistent optical names
12 - do not create rules on-the-fly, require explicit configuration
13 for netifs and optical drives
14 - properly document what system management needs to put
19 - remove deprecated trigger --type=failed logic
21 - remove deprecated BUS=, SYSFS{}=, ID= keys