Use Pthon 3.12 for meson coverage job

.github/workflows/buildwheel.yml

@@ -200,14 +200,14 @@ jobs:
       - run: bin/coverage_setuptools.sh
 
   # Test that we can make a coverage build and report coverage
-  test_coverage_build:
+  test_coverage_build_meson:
     name: Test coverage meson build
     runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: '3.13'
+          python-version: '3.12' # does not work with 3.13
       - run: sudo apt-get update
       - run: sudo apt-get install libflint-dev
       - run: pip install -r requirements-dev.txt

bin/coverage.sh

@@ -1,13 +1,5 @@
 #!/bin/bash
 #
-# This needs a patched Cython:
-#
-#   pip install git+https://github.com/oscarbenjamin/cython.git@pr_relative_paths
-#
-# That patch has been submitted as a pull request:
-#
-#   https://github.com/cython/cython/pull/6341
-#
 # Arguments to this script are passed to python -m flint.test e.g. to skip
 # doctests and run in quiet mode:
 #
@@ -18,9 +10,13 @@ set -o errexit
 RC="--rcfile=.coveragerc.meson"
 
 # See https://github.com/cython/cython/issues/6658
-# Needed for Python 3.13 only
+# Needed for Python 3.13 only but the plugin does not work with 3.13 anyway...
+#pip uninstall -y cython
+#pip install git+https://github.com/cython/cython.git@fdbca99
+
 pip uninstall -y cython
-pip install git+https://github.com/cython/cython.git@fdbca99
+pip install --pre cython       # unpinned to pick up new releases in CI
+# pip install cython==3.1.0a1  # known working version for Python < 3.13
 
 meson setup build -Dcoverage=true
 spin run -- coverage run $RC -m flint.test $@