(translation.E004) You have provided a value for the LANGUAGE_CODE setting that is not in the LANGUAGES setting.

     django3.0开始LANGUAGE_CODE前面必须配相应的LANGUAGES配置如下：

from django.utils.translation import gettext_lazy as _

LANGUAGES = [
    ('zh-Hans', _('Chinese')),
]

LANGUAGE_CODE = 'zh-Hans'