Upgrade pip

Author: jacobtylerwalls

.github/workflows/release-tests.yml

@@ -24,6 +24,7 @@ jobs:
           PIP_TRUSTED_HOST: "pypi.python.org pypi.org files.pythonhosted.org"
       - name: Create Python virtual environment with virtualenv==15.1.0
         run: |
+          python -m pip install pip --upgrade
           python -m pip install virtualenv==15.1.0
           python -m virtualenv venv2
           . venv2\scripts\activate