pin the Python version in the docker images

Dockerfile

@@ -1,4 +1,5 @@
-FROM python:3
+# Python 3.9.6
+FROM python@sha256:736b76eb3f64778646ce0051fb5fed4dfbf67016e51563946230ca8bb40ac687
 ENV PYTHONUNBUFFERED 1
 ADD . /code
 WORKDIR /code

docker-compose.yml

@@ -11,6 +11,7 @@ services:
 
   web:
     image: nebucatnetzer/network_inventory
+    # build: .
     volumes:
       - .:/code
     environment: