title: Django gettext doesn't works
body: <p>I try to serve my django-cms website in multiple languages</p>
  
  <p><em>makemessages</em> and <em>compilemessages</em> works like a charm, but when I <em>runserver</em> , my strings stay untranslated</p>
  
  <p>The python files where i used ugettext_lazy:</p>
  
  <pre><code>from cms.toolbar_pool import toolbar_pool
  from cms.extensions.toolbar import ExtensionToolbar
  from django.utils.translation import ugettext_lazy as _
  from .models import CategoryExtension
  
  
  @toolbar_pool.register
  class CategoryExtensionToolbar(ExtensionToolbar):
      # defines the model for the current toolbar
      model = CategoryExtension
  
      def populate(self):
          # setup the extension toolbar with permissions and sanity checks
          current_page_menu = self._setup_extension_toolbar()
  
          # if it's all ok
          if current_page_menu:
              # retrieves the instance of the current extension (if any) and the toolbar item URL
              page_extension, url = self.get_page_extension_admin()
              if url:
                  # adds a toolbar item in position 0 (at the top of the menu)
                  current_page_menu.add_modal_item(_('Page Category'), url=url,
                                                   disabled=not self.toolbar.edit_mode, position=0)
  </code></pre>
  
  <p>My settings related to translations : </p>
  
  <pre><code>def gettext(s):
      return s
  
  
  LOCALE_PATHS = (
      BASE_DIR + "/locale",
  )
  
  LANGUAGE_CODE = 'fr-fr'
  
  TIME_ZONE = 'Europe/Paris'
  
  USE_I18N = True
  
  USE_L10N = True
  
  USE_TZ = True
  
  LANGUAGES = (
      ('fr-fr', gettext('fr-fr')),
  )
  
  CMS_LANGUAGES = {
      1: [
          {
              'code': 'fr-fr',
              'name': gettext('fr-fr'),
              'redirect_on_fallback': True,
              'public': True,
              'hide_untranslated': False,
          },
      ],
      'default': {
          'redirect_on_fallback': True,
          'public': True,
          'hide_untranslated': False,
      },
  }
  </code></pre>
  
  <p>And my po file (in <em>PROJECT_ROOT/locale/fr-fr/LC_MESSAGES/django.po</em>) : </p>
  
  <pre><code># SOME DESCRIPTIVE TITLE.
  # Copyright (C) YEAR THE PACKAGE'S COPYRIGHT HOLDER
  # This file is distributed under the same license as the PACKAGE 
  # package.
  # FIRST AUTHOR &lt;EMAIL@ADDRESS&gt;, YEAR.
  #
  #, fuzzy
  msgid ""
  msgstr ""
  "Project-Id-Version: PACKAGE VERSION\n"
  "Report-Msgid-Bugs-To: \n"
  "POT-Creation-Date: 2017-06-06 19:11+0200\n"
  "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
  "Last-Translator: FULL NAME &lt;EMAIL@ADDRESS&gt;\n"
  "Language-Team: LANGUAGE &lt;LL@li.org&gt;\n"
  "Language: \n"
  "MIME-Version: 1.0\n"
  "Content-Type: text/plain; charset=UTF-8\n"
  "Content-Transfer-Encoding: 8bit\n"
  "Plural-Forms: nplurals=2; plural=(n &gt; 1);\n"
  
  #: myapp/cms_toolbars.py:22
  msgid "Page Category"
  msgstr "Catégorie de Page"
  
  #: myapp/configuration/cms_settings.py:6
  msgid "Page"
  msgstr "Page"
  
  #: myapp/configuration/cms_settings.py:7
  msgid "Page with instagram pictures"
  msgstr "Page avec bandeau instagram"
  
  #: myapp/configuration/cms_settings.py:8
  msgid "Page who list children"
  msgstr "Page qui liste ses enfants"
  
  #: myapp/configuration/i18n_settings.py:25
  #: myapp/configuration/i18n_settings.py:32
  msgid "fr-fr"
  msgstr "fr-fr"
  </code></pre>