"su user"를 통해 로그인을 시도할 때 이상한 오류가 발생합니다.

루트로 로그인하면 모든 것이 괜찮지만 user 또는 "su username" 명령을 사용하여 직접 로그인을 시도하면 이런 메시지가 나타납니다. 왜 이런 일이 일어나는지 궁금한 사람이 있습니까?

(1:43)# su username
    Traceback (most recent call last):
      File "/usr/bin/lshell", line 52, in <module>
        main()
      File "/usr/bin/lshell", line 38, in main
        userconf = CheckConfig(args).returnconf()
      File "/usr/local/lib/python2.7/dist-packages/lshell/checkconfig.py", line 71, in __init__
        self.get_config()
      File "/usr/local/lib/python2.7/dist-packages/lshell/checkconfig.py", line 286, in get_config
        self.get_config_sub('default')
      File "/usr/local/lib/python2.7/dist-packages/lshell/checkconfig.py", line 316, in get_config_sub
        conf = self.config.items(section) + conf
      File "/usr/lib/python2.7/dist-packages/backports/configparser/__init__.py", line 880, in items
        return [(option, value_getter(option)) for option in d.keys()]
      File "/usr/lib/python2.7/dist-packages/backports/configparser/__init__.py", line 877, in <lambda>
        section, option, d[option], d)
      File "/usr/lib/python2.7/dist-packages/backports/configparser/__init__.py", line 384, in before_get
        self._interpolate_some(parser, option, L, value, section, defaults, 1)
      File "/usr/lib/python2.7/dist-packages/backports/configparser/__init__.py", line 433, in _interpolate_some
        "found: %r" % (rest,))
    backports.configparser.InterpolationSyntaxError: '%' must be followed by '%' or '(', found: u"%u'"