Scaffolding command for new app fails due to lock file error

When I execute the command to scaffold a new app under macOS, I get the following error:

```sh
$ nix run github:holochain-open-dev/templates#hc-scaffold-app-template -- web-app
do you want to allow configuration setting 'extra-substituters' to be set to 'https://holochain-open-dev.cachix.org' (y/N)? y
do you want to permanently mark this value as trusted (y/N)? y
do you want to allow configuration setting 'extra-trusted-public-keys' to be set to 'holochain-open-dev.cachix.org-1:3Tr+9in6uo44Ga7qiuRIfOTFXog+2+YbyhwI/Z6Cp4U=' (y/N)? y
do you want to permanently mark this value as trusted (y/N)? y
error:
… while updating the lock file of flake 'github:holochain-open-dev/templates/aefe91aa3fae296e5c7e685fc413696f0adfb46c'

error: cannot write modified lock file of flake 'github:holochain-open-dev/templates' (use '--no-write-lock-file' to ignore)
```

Executing the same command with the suggested option succeeds
```sh
$ nix run github:holochain-open-dev/templates#hc-scaffold-app-template --no-write-lock-file -- web-app
```