what's the name price divisor for this epoch?
    Not all epochs have one---if this epoch does NOT have BLOCKSTACK_INT_DIVISION set,
    use get_epoch_price_multiplier() instead.

def get_epoch_price_divisor( block_height, namespace_id, units ):
    """
    what's the name price divisor for this epoch?
    Not all epochs have one---if this epoch does NOT have BLOCKSTACK_INT_DIVISION set,
    use get_epoch_price_multiplier() instead.
    """
    try:
        assert units in [TOKEN_TYPE_STACKS, 'BTC'], 'Unknown units {}'.format(units)
    except AssertionError as ae:
        log.exception(ae)
        log.error("FATAL: No such units {}".format(units))
        os.abort()

    divisor = 'PRICE_DIVISOR' if units == 'BTC' else 'PRICE_DIVISOR_STACKS'

    epoch_config = get_epoch_config( block_height )
    d = None

    if epoch_config['namespaces'].has_key(namespace_id):
        d = epoch_config['namespaces'][namespace_id][divisor]
    else:
        d = epoch_config['namespaces']['*'][divisor]

    try:
        assert d is not None
    except AssertionError as ae:
        log.exception(ae)
        log.error("FATAL: Tried to get a price divisor in an epoch without price divisors!")
        os.abort()

    return d