Use new, extended sponsors list in base template

pelicanconf.py

 from datetime import date
 
+TODAY = date.today()
+
 SPONSORS = [
     ("SpeedPartner", "/images/sponsors/speedpartner.png", "https://www.speedpartner.de", date(2038, 12, 31)),
     ("Informatik aktuell", "/images/sponsors/informatik_aktuell.png", "https://www.informatik-aktuell.de/", date(2021, 12, 31)),

templates/base.html

@@ -121,8 +121,10 @@
 			    {{ SPONSORSTEXTS[DEFAULT_LANG] }}
 			{% endif %}
 		    </p>
-                    {% for image, url in SPONSOR_LOGOS %}
-                        <a href="{{ url }}"><img src="{{ image }}" href="{{ url }}" alt="{{ url }}" class="sponsorslogo" /></a>
+                    {% for alt, image, url, before in SPONSOR_LOGOS %}
+		        {% if before >= TODAY %}
+                            <a href="{{ url }}"><img src="{{ image }}" href="{{ url }}" alt="{{ alt }}" title="{{ alt }}" class="sponsorslogo" /></a>
+		        {% endif %}
                     {% endfor %}
                 </div>
             </div>