Install missing virtualenv in GitHub workflow

.github/workflows/build.yml

@@ -37,7 +37,7 @@ on:
 
 jobs:
   rust-build:
-    name: ${{ matrix.name }}
+    name: Rust on ${{ matrix.name }}
 
     runs-on: ${{ matrix.os }}
 
@@ -144,7 +144,7 @@ jobs:
         uses: codecov/codecov-action@v3
 
   python-build:
-    name: ${{ matrix.name }}
+    name: Python ${{ matrix.python-version }} on ${{ matrix.name }}
 
     runs-on: ${{ matrix.os }}
 
@@ -171,12 +171,30 @@ jobs:
         uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.python-version }}
+          cache: 'pip'
+
+      - name: Create virtual environment for Maturin
+        run: python3 -m venv .venv
+
+      - name: Activate virtual environment on Linux and MacOS #source .venv/bin/activate
+        if: ${{ matrix.os != 'windows-latest' }}
+        run: echo ".venv/bin" >> $GITHUB_PATH
+
+      - name: Activate virtual environment on Windows #.venv\Scripts\activate.bat
+        if: ${{ matrix.os == 'windows-latest' }}
+        run: echo ".venv\Scripts" >> Out-File -FilePath $env:GITHUB_PATH -Encoding utf8 -Append
+
+      - name: Install Maturin
+        run: pip install maturin
 
       - name: Build Python extension and install pytest
-        uses: PyO3/maturin-action@v1
-        with:
-          command: develop
-          args: --extras=test
+        run: maturin develop --extras=test
+
+      #- name: Build Python extension and install pytest
+      #  uses: PyO3/maturin-action@v1
+      #  with:
+      #    command: develop
+      #    args: --extras=test
 
       - name: Run Python unit tests
         run: pytest tests/python/test_grex.py