Use explicit python version for Docker and Circle (#104)

We cache a virtualenv on CircleCI, and when there are new patch releases of Python and Circle upgrades, we have problems, because the cache's symlink for Python starts pointing to nowhere. This will help prevent that problem.

I figured it makes sense to lock down a specific version of Python in the Dockerfile while we’re at it.

Author: Mr0grog

.circleci/config.yml

@@ -1,9 +1,15 @@
 version: 2.1
+
+parameters:
+  python-version:
+    type: string
+    default: "3.7.13"
+
 jobs:
   build:
     working_directory: ~/web-monitoring-diff
     docker:
-      - image: cimg/python:3.7
+      - image: cimg/python:<< pipeline.parameters.python-version >>
     steps:
       - checkout
       - run:
@@ -15,11 +21,11 @@ jobs:
 
       - restore_cache:
           keys:
-            - cache-v2-{{ arch }}-{{ checksum "requirements.txt" }}-{{ checksum "requirements-server.txt" }}-{{ checksum "requirements-dev.txt" }}-{{ checksum "requirements-experimental.txt" }}
-            - cache-v2-{{ arch }}-{{ checksum "requirements.txt" }}-{{ checksum "requirements-server.txt" }}-{{ checksum "requirements-dev.txt" }}-
-            - cache-v2-{{ arch }}-{{ checksum "requirements.txt" }}-{{ checksum "requirements-server.txt" }}-
-            - cache-v2-{{ arch }}-{{ checksum "requirements.txt" }}-
-            - cache-v2-{{ arch }}-
+            - cache-v2-{{ arch }}-python<< pipeline.parameters.python-version >>-{{ checksum "requirements.txt" }}-{{ checksum "requirements-server.txt" }}-{{ checksum "requirements-dev.txt" }}-{{ checksum "requirements-experimental.txt" }}
+            - cache-v2-{{ arch }}-python<< pipeline.parameters.python-version >>-{{ checksum "requirements.txt" }}-{{ checksum "requirements-server.txt" }}-{{ checksum "requirements-dev.txt" }}-
+            - cache-v2-{{ arch }}-python<< pipeline.parameters.python-version >>-{{ checksum "requirements.txt" }}-{{ checksum "requirements-server.txt" }}-
+            - cache-v2-{{ arch }}-python<< pipeline.parameters.python-version >>-{{ checksum "requirements.txt" }}-
+            - cache-v2-{{ arch }}-python<< pipeline.parameters.python-version >>-
 
       # Bundle install dependencies
       - run:
@@ -32,7 +38,7 @@ jobs:
 
       # Store bundle cache
       - save_cache:
-          key: cache-v2-{{ arch }}-{{ checksum "requirements.txt" }}-{{ checksum "requirements-server.txt" }}-{{ checksum "requirements-dev.txt" }}-{{ checksum "requirements-experimental.txt" }}
+          key: cache-v2-{{ arch }}-python<< pipeline.parameters.python-version >>-{{ checksum "requirements.txt" }}-{{ checksum "requirements-server.txt" }}-{{ checksum "requirements-dev.txt" }}-{{ checksum "requirements-experimental.txt" }}
           paths:
             - venv
 
@@ -58,7 +64,8 @@ jobs:
     #         cd docs && make html
 
   build_docker:
-    machine: true
+    machine:
+      image: ubuntu-2004:202111-02
     steps:
       - checkout
       - run: |
@@ -74,7 +81,8 @@ jobs:
             - docker-image
 
   publish_docker:
-    machine: true
+    machine:
+      image: ubuntu-2004:202111-02
     steps:
       - attach_workspace:
           at: /tmp/workspace

Dockerfile

@@ -6,7 +6,7 @@
 # We separate them out so that the final `release` image can layer on top of
 # this one without needing compiler-related packages.
 ##
-FROM python:3.7-slim as base
+FROM python:3.7.13-slim as base
 LABEL maintainer="enviroDGI@gmail.com"
 
 RUN apt-get update && apt-get install -y --no-install-recommends \