test CircleCI machine executor (more RAM?)

.circleci/config.yml

@@ -3,8 +3,8 @@ version: 2
 jobs:
 
   build-python37:
-    docker:
+    machine:
-      - image: python:3.7
+      - image: ubuntu-2004:2023.02.1
     steps:
       - checkout
       - restore_cache:
@@ -20,8 +20,8 @@ jobs:
       - run: make smoke-test
 
   build-python38:
-    docker:
+    machine:
-      - image: python:3.8
+      - image: ubuntu-2004:2023.02.1
     steps:
       - checkout
       - restore_cache:
@@ -40,6 +40,5 @@ workflows:
   version: 2
   build:
     jobs:
-      #- build-python36
       - build-python37
       - build-python38