backupccl: add logging to backup manifest handling

Release note: None

pkg/ccl/backupccl/backupinfo/manifest_handling.go

@@ -164,21 +164,29 @@ func ReadBackupManifestFromStore(
 		// If we did not find `BACKUP_METADATA` we look for the
 		// `BACKUP_MANIFEST` file as it is possible the backup was created by a
 		// pre-23.1 node.
+		log.VInfof(ctx, 2, "could not find BACKUP_METADATA, falling back to BACKUP_MANIFEST")
 		backupManifest, backupManifestMemSize, backupManifestErr := ReadBackupManifest(ctx, mem, exportStore,
 			backupbase.BackupManifestName, encryption, kmsEnv)
 		if backupManifestErr != nil {
 			if !errors.Is(backupManifestErr, cloud.ErrFileDoesNotExist) {
-				return backuppb.BackupManifest{}, 0, err
+				return backuppb.BackupManifest{}, 0, backupManifestErr
 			}
 
 			// If we did not find a `BACKUP_MANIFEST` we look for a `BACKUP` file as
 			// it is possible the backup was created by a pre-20.1 node.
 			//
 			// TODO(adityamaru): Remove this logic once we disallow restores beyond
 			// the binary upgrade compatibility window.
+			log.VInfof(ctx, 2, "could not find BACKUP_MANIFEST, falling back to BACKUP")
 			oldBackupManifest, oldBackupManifestMemSize, oldBackupManifestErr := ReadBackupManifest(ctx, mem, exportStore,
 				backupbase.BackupOldManifestName, encryption, kmsEnv)
 			if oldBackupManifestErr != nil {
+				if errors.Is(oldBackupManifestErr, cloud.ErrFileDoesNotExist) {
+					log.VInfof(ctx, 2, "could not find any of the supported backup metadata files")
+					return backuppb.BackupManifest{}, 0,
+						errors.Wrapf(oldBackupManifestErr, "could not find BACKUP manifest file in any of the known locations: %s, %s, %s",
+							backupbase.BackupMetadataName, backupbase.BackupManifestName, backupbase.BackupOldManifestName)
+				}
 				return backuppb.BackupManifest{}, 0, oldBackupManifestErr
 			} else {
 				// We found a `BACKUP` manifest file.