ci: test: Install Python packages under virtual environment

This commit updates the CI workflow distribution bundle test job to
create a Python virtual environment and install the Python packages
required by the checked out Zephyr codebase in it.

Installing the Python packages in a virtual environment provides a
complete isolation from the runner host environment and prevents any
potential version incompatibilities and conflicts with the pre-
installed packages in the runner.

Note that Python virtual environment is not used for Linux because the
Linux build environment uses the CI Docker image that already has all
the required dependencies pre-installed.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>

.github/workflows/ci.yml

@@ -1233,7 +1233,6 @@ jobs:
 
     env:
       SUBSET_COUNT: 2
-      PYTHON_DEPS: https://raw.githubusercontent.com/zephyrproject-rtos/zephyr/main/scripts/requirements.txt
       ZEPHYR_TOOLCHAIN_VARIANT: zephyr
 
     steps:
@@ -1275,15 +1274,6 @@ jobs:
           brew install ccache coreutils dos2unix dtc gperf jq ninja wget
         fi
 
-        # Upgrade pip
-        sudo python3 -m pip install --upgrade pip
-
-        # Install west
-        sudo pip3 install --upgrade west
-
-        # Install required Python packages
-        sudo pip3 install --upgrade -r "${{ env.PYTHON_DEPS }}"
-
         # Set environment variables
         echo "TAR=gtar" >> $GITHUB_ENV
         echo "ARTIFACT_ROOT=${GITHUB_WORKSPACE}/artifacts" >> $GITHUB_ENV
@@ -1299,21 +1289,38 @@ jobs:
         # Install required system packages
         choco install ccache dtc-msys2 gperf jq ninja wget 7zip
 
-        # Upgrade pip
-        python3 -m pip install --upgrade pip
-
-        # Install west
-        pip3 install --upgrade west
-
-        # Install required Python packages
-        pip3 install --upgrade -r "${{ env.PYTHON_DEPS }}"
-
         # Enable long paths support for Git
         git config --system core.longpaths true
 
         # Set environment variables
         echo "ARTIFACT_ROOT=${GITHUB_WORKSPACE}/artifacts" >> $GITHUB_ENV
 
+    - name: Create Python virtual environment
+      if: ${{ runner.os != 'Linux' }}
+      run: |
+        # Create Python virtual environment
+        python3 -m venv ${GITHUB_WORKSPACE}/venv
+
+        # Resolve activation script path
+        if [ "${{ runner.os }}" == "Windows" ]; then
+          VENV_ACTIVATE="${GITHUB_WORKSPACE}/venv/Scripts/activate"
+        else
+          VENV_ACTIVATE="${GITHUB_WORKSPACE}/venv/bin/activate"
+        fi
+
+        # Test Python virtual environment
+        source ${VENV_ACTIVATE}
+        which python3
+        which pip3
+
+        # Install core components
+        python3 -m pip install --upgrade pip
+        pip3 install --upgrade setuptools wheel
+
+        # Set environment variables
+        echo "VENV=${GITHUB_WORKSPACE}/venv" >> $GITHUB_ENV
+        echo "VENV_ACTIVATE=${VENV_ACTIVATE}" >> $GITHUB_ENV
+
     - name: Download version information
       uses: actions/download-artifact@v3
       with:
@@ -1379,8 +1386,23 @@ jobs:
 
         popd
 
+    - name: Install west
+      run: |
+        # Activate Python virtual environment
+        if [ ! -z "${VENV_ACTIVATE}" ]; then
+          source ${VENV_ACTIVATE}
+        fi
+
+        # Install or upgrade west
+        pip3 install --upgrade west
+
     - name: Set up Zephyr repository
       run: |
+        # Activate Python virtual environment
+        if [ ! -z "${VENV_ACTIVATE}" ]; then
+          source ${VENV_ACTIVATE}
+        fi
+
         # Create Zephyr workspace
         ZEPHYR_WORKSPACE=${GITHUB_WORKSPACE}/zephyrproject
         west init ${ZEPHYR_WORKSPACE}
@@ -1406,8 +1428,25 @@ jobs:
         echo "ZEPHYR_WORKSPACE=${ZEPHYR_WORKSPACE}" >> $GITHUB_ENV
         echo "ZEPHYR_ROOT=${ZEPHYR_WORKSPACE}/zephyr" >> $GITHUB_ENV
 
+    - name: Install Python dependencies
+      run: |
+        # Activate Python virtual environment
+        if [ ! -z "${VENV_ACTIVATE}" ]; then
+          source ${VENV_ACTIVATE}
+
+          # Install Python dependencies from the checked out Zephyr repository
+          # if running inside a virtual environment; otherwise, it is assumed
+          # that the host already provides all the required dependencies.
+          pip3 install -r ${ZEPHYR_ROOT}/scripts/requirements.txt
+        fi
+
     - name: Run test suites
       run: |
+        # Activate Python virtual environment
+        if [ ! -z "${VENV_ACTIVATE}" ]; then
+          source ${VENV_ACTIVATE}
+        fi
+
         # Create working directory
         mkdir -p test
         cd test