'Subscribe current system to available pools matching the specified
regular expression
Raises:
* Exception - if error occurs while running command'

def subscribe(self, regexp):

    available_pools = RhsmPools(self.module)
    subscribed_pool_ids = []
    for pool in available_pools.filter(regexp):
        pool.subscribe()
        subscribed_pool_ids.append(pool.get_pool_id())
    return subscribed_pool_ids
