protected Path getTempSubFolder(final Path folder) throws Exception {
    return java.nio.file.Files.createTempDirectory(folder, null);
  }
Create a sub folder from the given path, that will not conflict with other folders.

@param folder the folder in which to create the sub folder
@return the path representing the sub folder
@throws Exception if the folder cannot be created
testutil/src/main/java/org/hyperledger/besu/kvstore/AbstractKeyValueStorageTest.java