'Load existing revision data from storage.'

def load_and_validate_existing(self, storage):

    self.document = storage.get_document(self.locale, self.slug)
    revision = storage.get_revision(self.revision_id)
    if (revision and self.document):
        if (revision.document == self.document):
            return (True, [])
        else:
            self.freshness = self.FRESH_NO
            raise self.SourceError(u'Revision    %s    is    for    Document    "%s",    expected    "%s".', self.revision_id, revision.document.get_absolute_url(), self.document.get_absolute_url())
    else:
        return (False, [])
