Merge pull request #275 from lsst/tickets/DM-41904

DM-41904: Enable python 3.12

.github/workflows/build.yaml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.11"]
+        python-version: ["3.11", "3.12"]
 
     steps:
       - uses: actions/checkout@v3

tests/test_executors.py

@@ -30,6 +30,7 @@
 
 import faulthandler
 import logging
+import multiprocessing
 import os
 import signal
 import sys
@@ -274,7 +275,6 @@ def test_mpexec_mp(self):
 
         methods = ["spawn"]
         if sys.platform == "linux":
-            methods.append("fork")
             methods.append("forkserver")
 
         for method in methods:
@@ -705,5 +705,15 @@ def test_clobber_outputs_execute(self) -> None:
         self.assertEqual(dataset_id_1, dataset_id_3)
 
 
+def setup_module(module):
+    """Force spawn to be used if no method given explicitly.
+
+    This can be removed when Python 3.14 changes the default.
+    """
+    multiprocessing.set_start_method("spawn", force=True)
+
+
 if __name__ == "__main__":
+    # Do not need to force start mode when running standalone.
+    multiprocessing.set_start_method("spawn")
     unittest.main()