FIX: Prevent setting access time after start time

Will close #405

RIGS/models.py

@@ -486,6 +486,10 @@ class Event(models.Model, RevisionMixin):
         if startEndSameDay and hasStartAndEnd and self.start_time > self.end_time:
             raise ValidationError('Unless you\'ve invented time travel, the event can\'t finish before it has started.')
 
+        accessAndStartSameDay = self.start_date == self.access_at.date()
+        if self.access_at.date() > self.start_date or (accessAndStartSameDay and self.access_at.time() > self.start_time):
+            raise ValidationError('Regardless of what some clients might think, access time cannot be after the event has started.')
+
     def save(self, *args, **kwargs):
         """Call :meth:`full_clean` before saving."""
         self.full_clean()