Update tested Python versions

Nothing actually uses Python 3.7, but 3.12 is becoming more common (especially
on Mac).

.github/workflows/pr-check.yml

@@ -24,11 +24,11 @@ jobs:
       matrix:
         python-version:
           - '3.6.8'   # slc7, slc8 and cs8 containers
-          - '3.7'
-          - '3.8'
-          - '3.9'
-          - '3.10'
+          - '3.8.10'  # ubuntu2004 container
+          - '3.9.16'  # slc9 container
+          - '3.10.6'  # ubuntu2204 container
           - '3.11'
+          - '3.12'
 
     steps:
       - uses: actions/checkout@v3

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 minversion = 3.20
-envlist = lint, py{27, 36, 37, 38, 39, 310, 311}, darwin
+envlist = lint, py{27, 36, 37, 38, 39, 310, 311, 312, 313}, darwin
 
 [gh-actions]
 # The "lint" job is run separately.
@@ -12,6 +12,8 @@ python =
     3.9: py39
     3.10: py310
     3.11: py311
+    3.12: py312
+    3.13: py313
 
 [testenv:lint]
 # Warning: This environment inherits settings from the main [testenv] section.