Use latest version of pip when running tests

Author: jamesls

.github/workflows/run-tests.yml

@@ -1,4 +1,4 @@
-name: Python package
+name: Run Tests
 
 on: [push]
 
@@ -19,6 +19,7 @@ jobs:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies
       run: |
+        pip install pip==20.0.2
         pip install -r requirements.txt
         python setup.py bdist_wheel
         pip install dist/*.whl