loadPrivateKey invokes log.Fatalln with a nil error if pem.Decode fails

[odeke-em]

If we examine in this section

ToRat/torat_server/crypto/crypto.go

Lines 25 to 28 in 5f90a79

	block, _ := pem.Decode(key)
	if block == nil {
	log.Fatalln("PrivateKey is not PEM format:", err)
	}

we can see this

But that's because that code incorrectly assumed that err would be returned after pem.Decode.