historian: declare rabbitmq exchange

Avoids a potential crash when serving gossip on greenlight.

Author: endothermicdev

archived/historian/historian.py

@@ -230,6 +230,7 @@ def rabbitmq_connect(self):
         params = pika.URLParameters(self.RABBITMQ_URL)
         self.connection = pika.BlockingConnection(params)  # default, localhost
         self.channel = self.connection.channel()
+        self.channel.exchange_declare(exchange='router.gossip', exchange_type='fanout')
         plugin.log(f"message queue connected to {params.host}:{params.port}")
 
     def run(self):