go/zodb/fs1: Fix index load from py3 data

Python3 emits index entries using bytes, but index.go was expecting only
bytestrings. As the result loading index produced by py3 was failing
e.g. as

    index_test.go:201: index load: testdata/py3_pickle3/1.fs.index: pickle @6: invalid oidPrefix: type ogórek.Bytes

-> Fix it by accepting both bytes and bytestrings inside the index.

go/zodb/storage/fs1/index.go

@@ -280,9 +280,9 @@ loop:
 
 		// decode oidPrefix
 		xoidPrefixStr := v[0]
-		oidPrefixStr, ok := xoidPrefixStr.(pickle.ByteString)
-		if !ok {
-			return nil, fmt.Errorf("invalid oidPrefix: type %T", xoidPrefixStr)
+		oidPrefixStr, err := pickle.AsBytes(xoidPrefixStr)
+		if err != nil {
+			return nil, fmt.Errorf("invalid oidPrefix: %s", err)
 		}
 		if l := len(oidPrefixStr); l != 6 {
 			return nil, fmt.Errorf("invalid oidPrefix: len = %d", l)
@@ -292,9 +292,9 @@ loop:
 
 		// check fsBucket
 		xkvStr := v[1]
-		kvStr, ok := xkvStr.(pickle.ByteString)
-		if !ok {
-			return nil, fmt.Errorf("invalid fsBucket: type %T", xkvStr)
+		kvStr, err := pickle.AsBytes(xkvStr)
+		if err != nil {
+			return nil, fmt.Errorf("invalid fsBucket: %s", err)
 		}
 		if l := len(kvStr); l%8 != 0 {
 			return nil, fmt.Errorf("invalid fsBucket: len = %d", l)

go/zodb/storage/fs1/index_test.go

@@ -196,9 +196,6 @@ func TestIndexLoadFromPy(t *testing.T) {
 	ztestdataReg.RunWithEach(t, _TestIndexLoadFromPy)
 }
 func _TestIndexLoadFromPy(t *testing.T, z *ZTestData) {
-	if z.Kind == "py3_pickle3" {
-		t.Skip("xfail")
-	}
 	fsiPy, err := LoadIndexFile(z.Path("1.fs.index"))
 	if err != nil {
 		t.Fatal(err)
@@ -268,9 +265,6 @@ func BenchmarkIndexLoad(b *testing.B) {
 	ztestdataReg.BenchWithEach(b, _BenchmarkIndexLoad)
 }
 func _BenchmarkIndexLoad(b *testing.B, z *ZTestData) {
-	if z.Kind == "py3_pickle3" {
-		b.Skip("xfail")
-	}
 	// FIXME small testdata/1.fs is not representative for benchmarks
 	for i := 0; i < b.N; i++ {
 		_, err := LoadIndexFile(z.Path("1.fs.index"))
@@ -308,9 +302,6 @@ func BenchmarkIndexGet(b *testing.B) {
 	ztestdataReg.BenchWithEach(b, _BenchmarkIndexGet)
 }
 func _BenchmarkIndexGet(b *testing.B, z *ZTestData) {
-	if z.Kind == "py3_pickle3" {
-		b.Skip("xfail")
-	}
 	// FIXME small testdata/1.fs is not representative for benchmarks
 	fsi, err := LoadIndexFile(z.Path("1.fs.index"))
 	if err != nil {