mariabackup.incremental_rocksdb failed in buildbot: cannot access the file

mariabackup.incremental_rocksdb          w1 [ fail ]  Found warnings/errors in server log file!

        Test ended at 2019-10-31 00:34:59

line

2019-10-31  0:34:59 0 [ERROR] LibRocksDB:[db_impl\db_impl_files.cc:283] [JOB 3] Failed to delete ./#rocksdb/MANIFEST-000006 type=3 #6 -- IO error: Failed to delete: ./#rocksdb/MANIFEST-000006: The process cannot access the file because it is being used by another process.

^ Found warnings in D:/winx64-packages/build/mysql-test/var/1/log/mysqld.1.err

ok