def __getattr__(self, attr):
     val = Thing.__getattr__(self, attr)
     if attr in ('start_date', 'end_date'):
         val = to_datetime(val)
         if not val.tzinfo:
             val = val.replace(tzinfo=g.tz)
     return val

    def is_roadblocked(cls, sr, start, end):
        rowkey = sr._id36
        start, end = map(to_date, [start, end])

        # retrieve columns for roadblocks starting before end
        try:
            columns = cls._cf.get(rowkey, column_finish=(to_datetime(end),),
                                  column_count=tdb_cassandra.max_column_count)
        except tdb_cassandra.NotFoundException:
            return False

        for key in columns.iterkeys():
            rb_start, rb_end = cls._dates_from_key(key)

            # check for overlap, end dates not inclusive
            if (start < rb_end) and (rb_start < end):
                return (rb_start, rb_end)
        return False

    def __getattr__(self, attr):
        val = super(PromoCampaign, self).__getattr__(attr)

        if attr == "total_budget_pennies" and hasattr(self, "bid") and not getattr(self, "bid_migrated", False):
            old_bid = int(super(PromoCampaign, self).__getattr__("bid") * 100)
            self.total_budget_pennies = old_bid
            self.bid_migrated = True
            return self.total_budget_pennies

        if attr == "bid_pennies" and hasattr(self, "cpm") and not getattr(self, "cpm_migrated", False):
            old_cpm = super(PromoCampaign, self).__getattr__("cpm")
            self.bid_pennies = old_cpm
            self.cpm_migrated = True
            return self.bid_pennies

        if attr in ("start_date", "end_date"):
            val = to_datetime(val)
            if not val.tzinfo:
                val = val.replace(tzinfo=g.tz)
        return val

    def __getattr__(self, attr):
        val = super(PromoCampaign, self).__getattr__(attr)

        if (attr == 'total_budget_pennies' and hasattr(self, 'bid') and
                not getattr(self, 'bid_migrated', False)):
            old_bid = int(super(PromoCampaign, self).__getattr__('bid') * 100)
            self.total_budget_pennies = old_bid
            self.bid_migrated = True
            return self.total_budget_pennies

        if (attr == 'bid_pennies' and hasattr(self, 'cpm') and
                not getattr(self, 'cpm_migrated', False)):
            old_cpm = super(PromoCampaign, self).__getattr__('cpm')
            self.bid_pennies = old_cpm
            self.cpm_migrated = True
            return self.bid_pennies

        if attr in ('start_date', 'end_date'):
            val = to_datetime(val)
            if not val.tzinfo:
                val = val.replace(tzinfo=g.tz)
        return val