django2: Replace assignment_tag with simple_tag

https://docs.djangoproject.com/en/2.0/releases/1.9/#assignment-tag

blueprint django2-support
Change-Id: Ib5021a4030fd9bc954365a352bdf4dccd049d28e

horizon/templatetags/branding.py

@@ -52,7 +52,7 @@ def site_branding_link():
 
 # TODO(jeffjapan): This is just an assignment tag version of the above, replace
 #                  when the dashboard is upgraded to a django version that
-#                  supports the @assignment_tag decorator syntax instead.
+#                  supports the @simple_tag decorator syntax instead.
 class SaveBrandingNode(template.Node):
     def __init__(self, var_name):
         self.var_name = var_name

horizon/templatetags/horizon.py

@@ -199,19 +199,19 @@ def jstemplate(parser, token):
     return JSTemplateNode(nodelist)
 
 
-@register.assignment_tag
+@register.simple_tag
 def load_config():
     return conf
 
 
-@register.assignment_tag
+@register.simple_tag
 def datepicker_locale():
     locale_mapping = getattr(settings, 'DATEPICKER_LOCALES',
                              bootstrap_datepicker.LOCALE_MAPPING)
     return locale_mapping.get(translation.get_language(), 'en')
 
 
-@register.assignment_tag
+@register.simple_tag
 def template_cache_age():
     return getattr(settings, 'NG_TEMPLATE_CACHE_AGE', 0)
 

openstack_dashboard/templatetags/context_selection.py

@@ -34,14 +34,14 @@ def is_multidomain_supported():
                     False))
 
 
-@register.assignment_tag(takes_context=True)
+@register.simple_tag(takes_context=True)
 def is_multi_region(context):
     if 'request' not in context:
         return False
     return is_multi_region_configured(context['request'])
 
 
-@register.assignment_tag
+@register.simple_tag
 def is_multidomain():
     return is_multidomain_supported()
 

openstack_dashboard/templatetags/themes.py

@@ -67,22 +67,22 @@ def find_asset(theme, asset):
     return staticfiles_storage.url(pathname2url(return_path))
 
 
-@register.assignment_tag()
+@register.simple_tag()
 def themes():
     return hz_themes.get_selectable_themes()
 
 
-@register.assignment_tag()
+@register.simple_tag()
 def theme_cookie():
     return hz_themes.get_theme_cookie_name()
 
 
-@register.assignment_tag()
+@register.simple_tag()
 def theme_dir():
     return hz_themes.get_theme_dir()
 
 
-@register.assignment_tag(takes_context=True)
+@register.simple_tag(takes_context=True)
 def current_theme(context):
     return get_theme(context.request)