be verbose around ~/virtualenv cache

.github/workflows/ci.yaml

@@ -167,6 +167,7 @@ jobs:
           sudo apt-get -f -y install libldap2-dev libsasl2-dev libssl-dev libyaml-dev ldap-utils
       - name: Install virtualenv
         run: |
+          set -x
           # Note: Use the verison of virtualenv pinned in fixed-requirements.txt so we
           #       only have to update it one place when we change the version
           # Note: Use --user to avoid polluting system site-packages (which breaks one of our tests)