DP-842 - use venv for b2 upload

Author: rhryckewicz

.github/workflows/ci_cd.yml

@@ -75,7 +75,7 @@ jobs:
         # upload to b2 (if credentials are provided, as they will be for backblaze's builds, but not pull requests)
         # This should be using python 3.8
         run: |
-          source env/bin/activate
+          source $GITHUB_WORKSPACE/env/bin/activate
           $GITHUB_WORKSPACE/maybe_upload_build_results ${{ env.OUTPUT_ZIP }}
 
       - name: Check GitHub Pages status