+# Create a virtualenv in a temporary directoy and write it down to used
+# or cleaned up later; cleanup is done in the script jjb-cleanup.sh.
+JJB_VENV="$(mktemp -d)"
+export JJB_VENV
+virtualenv "$JJB_VENV"
+echo "JJB_VENV=$JJB_VENV" > "$WORKSPACE/.jjb.properties"
+# shellcheck source=$VENV_DIR/bin/activate disable=SC1091
+source "$JJB_VENV/bin/activate"