Defined in github.com/btcsuite/btcd/blockchain/error.go
ErrUnexpectedDifficulty indicates specified bits do not align with the expected value either because it doesn't match the calculated valued based on difficulty regarted rules or it is out of the valid range.
ErrTimeTooNew: "ErrTimeTooNew", ErrDifficultyTooLow: "ErrDifficultyTooLow", ErrUnexpectedDifficulty: "ErrUnexpectedDifficulty", ErrHighHash: "ErrHighHash", ErrBadMerkleRoot: "ErrBadMerkleRoot",
str := fmt.Sprintf("block target difficulty of %064x is too low", target) return ruleError(ErrUnexpectedDifficulty, str) }
str := fmt.Sprintf("block target difficulty of %064x is "+ "higher than max of %064x", target, powLimit) return ruleError(ErrUnexpectedDifficulty, str) }