TFR protocol with private gitlab registry - misleading error when missing auth

[smills24]

Took a lot of frustration/trial and error to finally figure out this was actually related to auth so wanted to document it somewhere. I couldn't find much in the official docs about how to use this functionality.

To Reproduce

• Have a terraform module that has been published to a private gitlab registry (maybe any private registry, but I tested on gitlab specifically)
• Try to use it in terragrunt.hcl without configuring an auth token:

terraform {
    source = "tfr://gitlab.com/<GITLAB GROUP>/<MODULE NAME>/<MODULE_SYSTEM>?version=<VERSION>"
}

Init/plan/apply:

terragrunt plan --terragrunt-working-dir <DIR>

As expected, this fails. But it fails like this:

ERRO[0000] 1 error occurred:
        * error downloading 'tfr://gitlab.com/<GITLAB GROUP>/<MODULE NAME>/<MODULE_SYSTEM>?version=<VERSION>': Error downloading module from https://gitlab.com/api/v4/packages/terraform/modules/v1/<GITLAB GROUP>/<MODULE NAME>/<MODULE_SYSTEM>/<VERSION>/download: error receiving HTTP data

Hmm "error receiving HTTP data". Bit vague.

It works as expected if you do this, though:

TG_TF_REGISTRY_TOKEN=<TOKEN> terragrunt plan --terragrunt-working-dir <DIR>

Expected behavior An error message that makes it clear the "error receiving HTTP data" was because you were not authorized to :)

Versions

• Terragrunt version: 0.53.6
• Terraform version: 1.6.4
• Environment details (Ubuntu 20.04, Windows 10, etc.): mac os

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