Install dependencies in a virtualenv (#204)

Author: jku

action.yml

@@ -50,7 +50,7 @@ runs:
     - name: Run sigstore-conformance
       id: sigstore-conformance
       run: |
-        ${{ github.action_path }}/action.py
+        ./sigstore-conformance-env/bin/python ${{ github.action_path }}/action.py
       env:
         GHA_SIGSTORE_CONFORMANCE_ENVIRONMENT: "${{ inputs.environment }}"
         GHA_SIGSTORE_CONFORMANCE_ENTRYPOINT: "${{ inputs.entrypoint }}"

setup/setup.bash

@@ -28,4 +28,5 @@ min_vers=$(cut -d '.' -f2 <<< "${vers}")
 
 [[ "${maj_vers}" == "3" && "${min_vers}" -ge 7 ]] || die "Bad Python version: ${vers}"
 
-python -m pip install --requirement "${GITHUB_ACTION_PATH}/requirements.txt"
+python3 -m venv sigstore-conformance-env
+./sigstore-conformance-env/bin/python -m pip install --requirement "${GITHUB_ACTION_PATH}/requirements.txt"