Give abstract method the same signature as its overriding methods.
Give abstract method the same signature as its overriding methods.

ABC metaclass mechanisms do not check the signature of a method, only
its name, so this went undetected. It was also benign.

Signed-off-by: mulhern <7b51bcf507bcd7afb72bf8663752c0ddbeb517f6@redhat.com>

rvykydal/blivet,rvykydal/blivet,dwlehman/blivet,dwlehman/blivet,jkonecny12/blivet,rhinstaller/blivet,vojtechtrefny/blivet,jkonecny12/blivet,vpodzime/blivet,AdamWill/blivet,vpodzime/blivet,vojtechtrefny/blivet,rhinstaller/blivet,AdamWill/blivet