In order to let Nix evaluate the flake and enter the dev shell,
you may need to pull down private GitHub repos. Do this via the access-token
Nix config and gh auth login. Set the following in your RC of choice:
if command -v gh &>/dev/null && gh auth status &>/dev/null 2>&1; then
export NIX_CONFIG="access-tokens = github.com=$(gh auth token)"
fi