Fix failing tests in sdist workflows

Author: TomiBelan

.github/workflows/sdist.yml

@@ -2,7 +2,11 @@ name: sdist
 on: [push, pull_request]
 jobs:
   sdist:
-    runs-on: ubuntu-latest
+    # Avoid Ubuntu 24.04 in sdist workflows, because it contains libxmlsec1-dev
+    # v1.2.39, which has a bug that causes tests/test_pkcs11.py to fail.
+    # (It thinks the softhsm engine has a public key instead of a private key.)
+    # libxmlsec1 <=1.2.33 or >=1.2.42 works. TODO: Try 26.04 when available.
+    runs-on: ubuntu-22.04
     strategy:
       matrix:
         python: ["3.9", "3.10", "3.11", "3.12", "3.13"]

.github/workflows/wheels.yml

@@ -19,7 +19,11 @@ permissions: {}
 
 jobs:
   sdist:
-    runs-on: ubuntu-latest
+    # Avoid Ubuntu 24.04 in sdist workflows, because it contains libxmlsec1-dev
+    # v1.2.39, which has a bug that causes tests/test_pkcs11.py to fail.
+    # (It thinks the softhsm engine has a public key instead of a private key.)
+    # libxmlsec1 <=1.2.33 or >=1.2.42 works. TODO: Try 26.04 when available.
+    runs-on: ubuntu-22.04
 
     permissions:
       contents: write