fix logs doc_indexer failing + force python 3.9

Dockerfile

-FROM python:3-slim
+FROM python:3.9-slim
 
 WORKDIR /app
 

workers/doc_indexer.py

@@ -161,7 +161,7 @@ def index_docs(channel, method, properties, body):
         #logging.error(json.dumps(rep, indent=4))
         try:
             logging.error(json.dumps([
-                                        item.get("error", {}).get("reason") 
+                                        item.get("index", {}).get("error", {}).get("reason") 
                                         for item in rep.get("items", [])
                                      ],
                                      indent=4))