django format_html不能用string_concat

Question

我想向用户显示一个两行错误信息。我所做的所有尝试都失败了，我无法弄清楚这一点，尽管谷歌搜索了SO &。

我得到的错误是：

异常类型：IndexError

异常值：元组索引超出范围

这个问题似乎是使用format_html()与string_concat()。

这里是我的Python代码：

from django.utils import translation 
from django.utils.html import format_html 
from django.utils.translation import string_concat 
from django.utils.translation import ugettext_lazy as _ 
.... 
if not request.user.is_staff and language_versions_num_enabled > max_languages: 
    error_message = format_html(
     string_concat(
      _(u'You are only permitted <b>{}</b> <u>enabled</u> Language Versions for the selected <b>{}</b> subscription plan.'), 
      ' <icon class="fa fa-frown-o icon_size26 icon_padding"></icon>', 
      '<br /><br />', 
      _(u'Either select a different subscription plan or disable <b>{}</b> of your <b>{}</b> <u>enabled</u> Language Versions.'.format(max_languages, stripe_plan['title'], language_versions_num_enabled-max_languages, language_versions_num_enabled)) 
     ) 
    ) 
    messages.add_message(request, messages.ERROR, error_message) 
else: 

我真的很希望有人能指出我在做什么错在这里。

编辑

我使用Django 1.10和Python 3.5.2。

这里是堆栈跟踪：

Environment: 


Request Method: POST 
Request URL: http://127.0.0.1:8000/subscription/subscription/ 

Django Version: 1.10.5 
Python Version: 3.5.2 
Installed Applications: 
('django.contrib.admin', 
'django.contrib.auth', 
'django.contrib.contenttypes', 
'django.contrib.humanize', 
'django.contrib.messages', 
'django.contrib.sessions', 
'django.contrib.sites', 
'django.contrib.sitemaps', 
'django.contrib.staticfiles', 
'admin_honeypot', 
'axes', 
'rest_framework', 
'rest_framework.authtoken', 
'captcha', 
'my_app.contact', 
'djstripe', 
'my_app.common', 
'my_app.users', 
'my_app.core', 
'imagekit', 
'parsley', 
'registration', 
'templatetag_handlebars', 
'settings_context_processor', 
'crispy_forms', 
'lockdown', 
'rosetta', 
'raven.contrib.django.raven_compat') 
Installed Middleware: 
('raven.contrib.django.middleware.SentryMiddleware', 
'django.middleware.security.SecurityMiddleware', 
'django.contrib.sessions.middleware.SessionMiddleware', 
'django.contrib.auth.middleware.AuthenticationMiddleware', 
'my_app.users.middleware.LocaleOverrideMiddleware', 
'django.middleware.locale.LocaleMiddleware', 
'my_app.users.middleware.AdminLocaleMiddleware', 
'django.middleware.common.CommonMiddleware', 
'django.middleware.csrf.CsrfViewMiddleware', 
'django.contrib.messages.middleware.MessageMiddleware', 
'django.middleware.clickjacking.XFrameOptionsMiddleware', 
'lockdown.middleware.LockdownMiddleware') 



Traceback: 

File "C:\Users\laptop\desktop\my_app\env3\lib\site-packages\django\core\handlers\exception.py" in inner 
    39.    response = get_response(request) 

File "C:\Users\laptop\desktop\my_app\env3\lib\site-packages\django\core\handlers\base.py" in _legacy_get_response 
    249.    response = self._get_response(request) 

File "C:\Users\laptop\desktop\my_app\env3\lib\site-packages\django\core\handlers\base.py" in _get_response 
    187.     response = self.process_exception_by_middleware(e, request) 

File "C:\Users\laptop\desktop\my_app\env3\lib\site-packages\django\core\handlers\base.py" in _get_response 
    185.     response = wrapped_callback(request, *callback_args, **callback_kwargs) 

File "C:\Users\laptop\desktop\my_app\env3\lib\site-packages\django\contrib\auth\decorators.py" in _wrapped_view 
    23.     return view_func(request, *args, **kwargs) 

File "C:\Users\laptop\desktop\my_app\env3\lib\site-packages\django\views\decorators\http.py" in inner 
    40.    return func(request, *args, **kwargs) 

File "C:\Users\laptop\desktop\my_app\my_app\core\decorators.py" in wrapper 
    21.    return f(request, *args, **kwargs) 

File "C:\Users\laptop\desktop\my_app\my_app\core\views\user_settings_views.py" in subscription 
    402.         _(u'Either select a different subscription plan or disable <b>{}</b> of your <b>{}</b> <u>enabled</u> Language Versions.'.format(max_languages, stripe_plan['title'], language_versions_num_enabled-max_languages, language_versions_num_enabled)) 

File "C:\Users\laptop\desktop\my_app\env3\lib\site-packages\django\utils\html.py" in format_html 
    106.  return mark_safe(format_string.format(*args_safe, **kwargs_safe)) 

File "C:\Users\laptop\desktop\my_app\env3\lib\site-packages\django\utils\functional.py" in __wrapper__ 
    112.     return getattr(res, method_name)(*args, **kw) 

Exception Type: IndexError at /subscription/subscription/ 
Exception Value: tuple index out of range 

Answer 1

你把格式错了地方。试试这个：

error_message = format_html(
    string_concat(
     _(u'You are only permitted <b>{}</b> <u>enabled</u> Language Versions for the selected <b>{}</b> subscription plan.'), 
     ' <icon class="fa fa-frown-o icon_size26 icon_padding"></icon>', 
     '<br /><br />', 
     _(u'Either select a different subscription plan or disable <b>{}</b> of your <b>{}</b> <u>enabled</u> Language Versions.') 
    ).format(max_languages, stripe_plan['title'], language_versions_num_enabled-max_languages, language_versions_num_enabled) 
)