cI: attempt again again to use uv to install python

Author: psychedelicious

.github/workflows/python-tests.yml

@@ -59,9 +59,6 @@ jobs:
     name: 'py${{ matrix.python-version }}: ${{ matrix.platform }}'
     runs-on: ${{ matrix.os }}
     timeout-minutes: 15 # expected run time: 2-6 min, depending on platform
-    env:
-      PIP_USE_PEP517: '1'
-      UV_SYSTEM_PYTHON: 1
 
     steps:
       - name: checkout
@@ -89,13 +86,13 @@ jobs:
 
       - name: install python
         if: ${{ steps.changed-files.outputs.python_any_changed == 'true' || inputs.always_run == true }}
-        run: uv python install ${{ matrix.python-version }}
+        run: uv python install ${{ matrix.python-version }} --preview --verbose
 
       - name: install dependencies
         if: ${{ steps.changed-files.outputs.python_any_changed == 'true' || inputs.always_run == true }}
         env:
           UV_INDEX: ${{ matrix.extra-index-url }}
-        run: uv pip install --editable ".[test]"
+        run: uv pip install --editable ".[test]" --system --verbose
 
       - name: run pytest
         if: ${{ steps.changed-files.outputs.python_any_changed == 'true' || inputs.always_run == true }}