private void deleteEnvFile(final String filename) {
        final Path file = envDir.resolve(filename);
        if (Files.isRegularFile(file)) {
            try {
                LOGGER.info("Deleting file {}", FileUtil.getCanonicalPath(file));
                Files.delete(file);
            } catch (IOException e) {
                throw new RuntimeException("Unable to delete file: " + FileUtil.getCanonicalPath(file));
            }
        } else {
            LOGGER.error("LMDB env file {} doesn't exist", FileUtil.getCanonicalPath(file));
        }
    }
Deletes {@link LmdbEnv} from the filesystem if it is already closed.
stroom-lmdb/src/main/java/stroom/lmdb2/LmdbEnvDir.java