Create internal connection to AMQP service.

def connect(self):
        """
        Create internal connection to AMQP service.
        """
        logging.info("Connecting to {} with user {}.".format(self.host, self.username))
        credentials = pika.PlainCredentials(self.username, self.password)
        connection_params = pika.ConnectionParameters(host=self.host,
                                                      credentials=credentials,
                                                      heartbeat_interval=self.heartbeat_interval)
        self.connection = pika.BlockingConnection(connection_params)