'Get the date of the user\'s last contribution.'

@property
def last_contribution_date(self):

    from kitsune.customercare.models import Reply
    from kitsune.questions.models import Answer
    from kitsune.wiki.models import Revision
    dates = []
    try:
        aoa_reply = Reply.objects.filter(user=self.user).latest('created')
        dates.append(aoa_reply.created)
    except Reply.DoesNotExist:
        pass
    try:
        answer = Answer.objects.filter(creator=self.user).latest('created')
        dates.append(answer.created)
    except Answer.DoesNotExist:
        pass
    try:
        revision = Revision.objects.filter(creator=self.user).latest('created')
        dates.append(revision.created)
    except Revision.DoesNotExist:
        pass
    try:
        revision = Revision.objects.filter(reviewer=self.user).latest('reviewed')
        dates.append((revision.reviewed or revision.created))
    except Revision.DoesNotExist:
        pass
    if (len(dates) == 0):
        return None
    return max(dates)
