Hi,
the method Connection.send_cmd_all() (pool.py) calls host.mark_dead(msg) on a socket.error: but the Host class doesn't implement such method, so the AttributeError is raised.
I have written this method in the Host class (host.py):
def mark_dead(self, msg):
logging.error(msg)
self.close_socket()
I don't know if this could be a solution, but it seems to work.