Install pytest in Github actions

Author: chadsec1

.github/workflows/tests.yml

@@ -28,7 +28,9 @@ jobs:
           cd liboqs-python
           pip install .
       - name: Install Python dependencies
-        run: pip install -r requirements.txt
+        run: |
+          pip install -r requirements.txt
+          pip install pytest
 
       - name: Run tests
         run: pytest --maxfail=1 --disable-warnings -q