go/zodb/zeo: Make "no serial on load after object deleted" to be a known bug

This turns zeo tests to pass.
The bug is reported upstream here: https://github.com/zopefoundation/ZODB/issues/318

go/internal/xtesting/xtesting.go

@@ -211,17 +211,22 @@ func LoadDBHistory(zurl string) (_ []Txn, err error) {
 }
 
 // checkLoad verifies that zdrv.Load(xid) returns expected result.
-func checkLoad(t *testing.T, zdrv zodb.IStorageDriver, xid zodb.Xid, expect objState) {
+func checkLoad(t *testing.T, zdrv zodb.IStorageDriver, xid zodb.Xid, expect objState, bugs map[string]bool) {
 	t.Helper()
 	buf, tid, err := zdrv.Load(context.Background(), xid)
 
 	// deleted obj - it should load with "no data"
 	if expect.data == nil {
+		var eNoData error = &zodb.NoDataError{Oid: xid.Oid, DeletedAt: expect.tid}
+		if bugs["load:noserial-after-deleted"] {
+			// https://github.com/zopefoundation/ZODB/issues/318
+			eNoData = &zodb.NoObjectError{Oid: xid.Oid}
+		}
 		errOk := &zodb.OpError{
 			URL:  zdrv.URL(),
 			Op:   "load",
 			Args: xid,
-			Err:  &zodb.NoDataError{Oid: xid.Oid, DeletedAt: expect.tid},
+			Err:  eNoData,
 		}
 		if !reflect.DeepEqual(err, errOk) {
 			t.Errorf("load %v: returned err unexpected:\nhave: %v\nwant: %v", xid, err, errOk)
@@ -258,7 +263,12 @@ func checkLoad(t *testing.T, zdrv zodb.IStorageDriver, xid zodb.Xid, expect objS
 // DrvTestLoad verifies that zdrv implements Load correctly.
 //
 // txnvOk is what data to expect to be in the database.
-func DrvTestLoad(t *testing.T, zdrv zodb.IStorageDriver, txnvOk []Txn) {
+func DrvTestLoad(t *testing.T, zdrv zodb.IStorageDriver, txnvOk []Txn, bugv ...string) {
+	bugs := map[string]bool{}
+	for _, bug := range bugv {
+		bugs[bug] = true
+	}
+
 	// current knowledge of what was "before" for an oid as we scan over
 	// data base entries
 	before := map[zodb.Oid]objState{}
@@ -273,13 +283,13 @@ func DrvTestLoad(t *testing.T, zdrv zodb.IStorageDriver, txnvOk []Txn) {
 
 			// ~ loadSerial
 			xid := zodb.Xid{txh.Tid, obj.Oid}
-			checkLoad(t, zdrv, xid, objState{txh.Tid, obj.Data})
+			checkLoad(t, zdrv, xid, objState{txh.Tid, obj.Data}, bugs)
 
 			// ~ loadBefore
 			xid = zodb.Xid{txh.Tid - 1, obj.Oid}
 			expect, ok := before[obj.Oid]
 			if ok {
-				checkLoad(t, zdrv, xid, expect)
+				checkLoad(t, zdrv, xid, expect, bugs)
 			}
 
 			before[obj.Oid] = objState{txh.Tid, obj.Data}
@@ -291,7 +301,7 @@ func DrvTestLoad(t *testing.T, zdrv zodb.IStorageDriver, txnvOk []Txn) {
 	// XXX should we get "no such transaction" with at > head? - yes
 	for oid, expect := range before {
 		xid := zodb.Xid{zodb.TidMax, oid}
-		checkLoad(t, zdrv, xid, expect)
+		checkLoad(t, zdrv, xid, expect, bugs)
 	}
 
 	// XXX verify load of non-existing object

go/zodb/storage/zeo/zeo_test.go

@@ -44,6 +44,7 @@ type ZEOSrv interface {
 	Close() error
 
 	Encoding() encoding // encoding used on the wire - 'M' or 'Z'
+	Bugs() []string     // list of known server bugs
 }
 
 // ZEOPySrv represents running ZEO/py server.
@@ -58,6 +59,14 @@ type ZEOPySrv struct {
 	errExit error		// error from Wait
 }
 
+func (_ *ZEOPySrv) Bugs() []string {
+	return []string{
+		// ZODB/py does not return serial for loadBefore after object was deleted
+		// https://github.com/zopefoundation/ZODB/issues/318
+		"load:noserial-after-deleted",
+	}
+}
+
 type ZEOPyOptions struct {
 	msgpack bool // whether to advertise msgpack
 }
@@ -202,7 +211,7 @@ func withZEOSrv(t *testing.T, f func(t *testing.T, zsrv ZEOSrv), optv ...tOption
 }
 
 // withZEO tests f on all kinds of ZEO servers connected to by ZEO client.
-func withZEO(t *testing.T, f func(t *testing.T, zdrv *zeo), optv ...tOptions) {
+func withZEO(t *testing.T, f func(t *testing.T, zsrv ZEOSrv, zdrv *zeo), optv ...tOptions) {
 	t.Helper()
 	withZEOSrv(t, func(t *testing.T, zsrv ZEOSrv) {
 		t.Helper()
@@ -212,7 +221,7 @@ func withZEO(t *testing.T, f func(t *testing.T, zdrv *zeo), optv ...tOptions) {
 			err := zdrv.Close(); X(err)
 		}()
 
-		f(t, zdrv)
+		f(t, zsrv, zdrv)
 	}, optv...)
 }
 
@@ -239,8 +248,8 @@ func TestLoad(t *testing.T) {
 	data := "../fs1/testdata/1.fs"
 	txnvOk, err := xtesting.LoadDBHistory(data); X(err)
 
-	withZEO(t, func(t *testing.T, z *zeo) {
-		xtesting.DrvTestLoad(t, z, txnvOk)
+	withZEO(t, func(t *testing.T, zsrv ZEOSrv, z *zeo) {
+		xtesting.DrvTestLoad(t, z, txnvOk, zsrv.Bugs()...)
 	}, tOptions{
 		Preload: data,
 	})