Noisy error from rattler_repodata_gateway::fetch

[wolfv]

When fetching repodata it's "OK" if the target architecture is missing - the only required file is the noarch/repodata.json basically.

However, fetch_repodata returns a NotFound error for non-noarch files. The problem is that this is logged through the instrument attribute on the fetch_repo_data function and pops up in the logs (e.g. in rattler-build).

I am wondering if we could either disable logging an error for this particular error or if we should return a None instead.