Switch to using a virtualenv for tests

Author: jrha

.github/workflows/pytest.yml

@@ -16,12 +16,13 @@ jobs:
         fetch-depth: 0
     - name: Install Python
       run: |
-        dnf install -y python3 python3-pip
+        dnf install -y python3
     - name: Install dependencies
       run: |
-        python3 -m pip install --upgrade pip
-        pip3 install -r requirements.txt
-        pip3 install -r test_requirements.txt
+        python3 -m venv /tmp/venv
+        /tmp/venv/bin/pip install --upgrade pip
+        /tmp/venv/bin/pip install -r requirements.txt
+        /tmp/venv/bin/pip install -r test_requirements.txt
     - name: Running unit tests with pytest
       run: |
-        cd aquilon/ && pytest -vv
+        cd aquilon/ && /tmp/venv/bin/pytest -vv