keys: change Signature() and Address() to not return errors

As they never can return any real one.

pkg/crypto/keys/private_key.go

@@ -125,7 +125,7 @@ func (p *PrivateKey) Address() (string, error) {
 	if err != nil {
 		return "", err
 	}
-	return pk.Address()
+	return pk.Address(), nil
 }
 
 // Signature creates the signature using the private key.
@@ -134,7 +134,7 @@ func (p *PrivateKey) Signature() ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
-	return pk.Signature()
+	return pk.Signature(), nil
 }
 
 // Sign signs arbitrary length data using the private key.

pkg/crypto/keys/publickey.go

@@ -168,32 +168,25 @@ func (p *PublicKey) EncodeBinary(w io.Writer) error {
 	return binary.Write(w, binary.LittleEndian, p.Bytes())
 }
 
-func (p *PublicKey) Signature() ([]byte, error) {
+func (p *PublicKey) Signature() []byte {
 	b := p.Bytes()
 	b = append([]byte{0x21}, b...)
 	b = append(b, 0xAC)
 
 	sig := hash.Hash160(b)
 
-	return sig.Bytes(), nil
+	return sig.Bytes()
 }
 
-func (p *PublicKey) Address() (string, error) {
-	var (
-		err error
-		b   []byte
-	)
-	if b, err = p.Signature(); err != nil {
-		return "", err
-	}
+func (p *PublicKey) Address() string {
+	var b []byte = p.Signature()
 
 	b = append([]byte{0x17}, b...)
-
 	csum := hash.Checksum(b)
 	b = append(b, csum...)
 
 	address := crypto.Base58Encode(b)
-	return address, nil
+	return address
 }
 
 // Verify returns true if the signature is valid and corresponds

pkg/crypto/keys/publickey_test.go

@@ -42,7 +42,7 @@ func TestDecodeFromString(t *testing.T) {
 func TestPubkeyToAddress(t *testing.T) {
 	pubKey, err := NewPublicKeyFromString("031ee4e73a17d8f76dc02532e2620bcb12425b33c0c9f9694cc2caa8226b68cad4")
 	assert.Nil(t, err)
-	actual, _ := pubKey.Address()
+	actual := pubKey.Address()
 	expected := "AUpGsNCHzSimeMRVPQfhwrVdiUp8Q2N2Qx"
 	assert.Equal(t, expected, actual)
 }