uv ignores the env var

.github/workflows/tests.yml

@@ -300,17 +300,17 @@ jobs:
           uv venv
           # cffi will probably have no public release until a beta or even RC
           # version of Python 3.13, see https://github.com/python-cffi/cffi/issues/23
-          echo 'cffi @ git+https://github.com/python-cffi/cffi.git@954cab4f889fb019a7f90df153ee1be501495f58 ; platform_python_implementation == "CPython"' > cffi_constraint.txt
+          uv pip install git+https://github.com/python-cffi/cffi.git@954cab4f889fb019a7f90df153ee1be501495f58#cffi
           # coverage has a wheel on PyPI for a future python version which is
           # not ABI compatible with the current one, so build it from sdist:
-          pip install -U --no-binary :all: coverage
+          uv pip install -U --no-binary :all: coverage
           # Unzip into src/ so that testrunner can find the .so files
           # when we ask it to load tests from that directory. This
           # might also save some build time?
           unzip -n dist/AccessControl-*whl -d src
           # Use "--pre" here because dependencies with support for this future
           # Python release may only be available as pre-releases
-          PIP_CONSTRAINT=$PWD/cffi_constraint.txt uv pip install --pre -U -e .[test]
+          uv pip install --pre -U -e .[test]
       - name: Install AccessControl
         if: ${{ !startsWith(matrix.python-version, '3.13.0-alpha - 3.13.0') }}
         run: |