Actually there is a little wiggle room Harley, and it simply isn't as clear as you would like it to be. The verse says that he is not a son of man that he should repent. All sons of men are required to repent, but not all do. God is not required to repent, as man is. But apparently he did.
"Also the Glory of Israel will not lie or change His mind; for He is not a man that He should change His mind." 1 Sam 15:29