actually it is over there

ci-tools/update-nixpkgs

 #!/usr/bin/env nix-shell
-#!nix-shell -i sh -p nixUnstable git curl
+#!nix-shell -i sh -p nixUnstable git curl python3
 
 set -eux -o pipefail
 
@@ -10,7 +10,7 @@ nix-build -A morph -o result-before
 
 git checkout "${TARGET_BRANCH}" || git checkout -b "${TARGET_BRANCH}"
 
-./update-nixpkgs
+./tools/update-nixpkgs
 nix-build -A morph -o result-after
 diff=$(nix --extra-experimental-features nix-command store diff-closures ./result-before/ ./result-after/)