handle exception vevent without summary (#25887)

chrono/agendas/models.py

@@ -493,7 +493,10 @@ class Desk(models.Model):
         with transaction.atomic():
             update_datetime = now()
             for vevent in parsed.contents.get('vevent', []):
-                summary = force_text(vevent.contents['summary'][0].value)
+                if 'summary' in vevent.contents:
+                    summary = force_text(vevent.contents['summary'][0].value)
+                else:
+                    summary = _('Exception')
                 try:
                     start_dt = vevent.dtstart.value
                     if not isinstance(start_dt, datetime.datetime):

tests/test_agendas.py

@@ -31,7 +31,6 @@ UID:950c3ff889d2465dd5d648c4c2194232c0a565f4
 DTSTART:20170830T180800Z
 DTEND:20170831T223400Z
 SEQUENCE:2
-SUMMARY:Event 2
 END:VEVENT
 END:VCALENDAR"""