fix: skip empty repositories instead of crashing

[wjglerum]

Problem

When Evergreen iterates over an organization that contains an empty repository (one created but never pushed to, so it has no commits), the run crashes:

github.GithubException.GithubException: This repository is empty.: 404
{"message": "This repository is empty.",
 "documentation_url": "https://docs.github.com/v3/repos/contents/#get-contents",
 "status": "404"}

check_optional_file() in exceptions.py calls repo.get_contents(...) to look for an existing dependabot.yml. For a repo where the file merely does not exist, PyGithub raises UnknownObjectException, which is caught and translated to OptionalFileNotFoundError. But for an empty repository, GitHub returns a 404 that PyGithub surfaces as the base GithubException ("This repository is empty."), not UnknownObjectException. That escapes the existing handler and aborts the whole run, so no other repositories in the org get processed.

Fix

Handle a 404 GithubException the same way as a missing optional file, so the repository is treated as having no config and skipped by the normal flow. Non-404 GithubExceptions (permissions, rate limits, server errors) are re-raised unchanged so genuine problems are not masked.

Tests

Added two cases to test_exceptions.py:

• an empty-repository 404 (base GithubException) is translated to OptionalFileNotFoundError
• a non-404 GithubException (e.g. 403) is re-raised unchanged

All existing tests still pass.

[Copilot]

Pull request overview

This PR improves robustness when scanning GitHub organizations by preventing Evergreen from crashing on empty repositories (repositories with no commits) when checking for optional configuration files via PyGithub.

Changes:

• Extend check_optional_file() to translate 404 GithubException (empty repo case) into OptionalFileNotFoundError.
• Add unit tests covering the empty-repository 404 translation and ensuring non-404 GithubExceptions are still re-raised.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
exceptions.py	Adds handling for base GithubException 404s (empty repos) to match existing optional-file behavior.
test_exceptions.py	Adds test coverage for empty-repository 404 behavior and non-404 re-raise behavior.