Fix escaping error in blog demo

Closes #726.

demos/blog/templates/base.html

@@ -15,7 +15,7 @@
             <a href="/compose">{{ _("New post") }}</a> -
             <a href="/auth/logout?next={{ url_escape(request.uri) }}">{{ _("Sign out") }}</a>
           {% else %}
-            {{ _('<a href="%(url)s">Sign in</a> to compose/edit') % {"url": "/auth/login?next=" + url_escape(request.uri)} }}
+            {% raw _('<a href="%(url)s">Sign in</a> to compose/edit') % {"url": "/auth/login?next=" + url_escape(request.uri)} %}
           {% end %}
         </div>
         <h1><a href="/">{{ escape(handler.settings["blog_title"]) }}</a></h1>