'Adds a connection to the pool of connections that can be
reused for the named host.'

def put_http_connection(self, host, port, is_secure, conn):

    with self.mutex:
        key = (host, port, is_secure)
        if (key not in self.host_to_pool):
            self.host_to_pool[key] = HostConnectionPool()
        self.host_to_pool[key].put(conn)
