Fixed #16350 -- Forced capitalization in template.

This improves rendering in some foreign languages.

django/contrib/admin/templates/admin/base.html

@@ -53,7 +53,7 @@
     {% block messages %}
         {% if messages %}
         <ul class="messagelist">{% for message in messages %}
-          <li{% if message.tags %} class="{{ message.tags }}"{% endif %}>{{ message }}</li>
+          <li{% if message.tags %} class="{{ message.tags }}"{% endif %}>{{ message|capfirst }}</li>
         {% endfor %}</ul>
         {% endif %}
     {% endblock messages %}