LexException: f-string: trailing junk in field

Question

In doing the following, I'm getting the error LexException: f-string: trailing junk in field:

(nixos-install #* ctx.args
               :I (with [f (open (+ resources "/flake.lock"))]
                        f"nixpkgs=https://github.com/nixos/nixpkgs/archive/{(D (.load json f)).nodes.nixos-22-05.locked.rev}.tar.gz")
               :m/run True
               :show-trace True
               :install-bootloader install-bootloader
               :option "tarball-ttl 0")

What exactly does this mean?