Return the list of files in a directory, assuming that our user can read it.

def _listdir(self, path):
        """Return the list of files in a directory, assuming that our user can read it."""
        if self._user is None:
            return os.listdir(path)
        else:
            args = self._build_cmdline(['/bin/ls', '-1A', path])
            return subprocess.check_output(args, stderr=DEVNULL).decode('utf-8', errors='ignore').split('\n')