Howto reference a custom package from a manifest

[Timothy Washington]

I successfully installed a custom rust package (see "*Howto supply
cargo-build-system dependency to guix package definition*
<https://lists.gnu.org/archive/html/help-guix/2023-05/msg00009.html>").

It is located in
/gnu/store/10sivvy746n5jdnsgny5afxpwa5yzy5f-rust-rustscan-2.1.1/bin/rustscan

It's definition is
(define-public rust-rustscan-2
  (package
    (name "rust-rustscan")
    (version "2.1.1")
    ...))

But I'm getting a failure when trying to reference it in a local profile,
using specifications->manifest

A. How do I get more detail on the error, in order to troubleshoot. --debug
isn't yielding anything

B. How do I make rust-rustscan (my custom build of a rust package),
available in a global profile.


# guix/packages/manifest.scm
(specifications->manifest '("rust-rustscan-2"))  ;; Also fails...
(specifications->manifest '("rust-rustscan"))

# bash
$ guix package -m guix/packages/manifest.scm
guix package: error: rust-rustscan-2: unknown package
guix package: error: failed to load 'guix/packages/manifest.scm':
gnu/packages.scm:551:4: In procedure specification->package+output:

$ guix package -m guix/packages/manifest.scm --debug=5
guix package: error: rust-rustscan: unknown package
guix package: error: failed to load 'guix/packages/manifest.scm':
gnu/packages.scm:551:4: In procedure specification->package+output:
Throw to key `quit' with args `(1)'.

Tim