[3.12] gh-112414: Fix `AttributeError` when calling `repr()` on a namespace package imported with a custom loader (GH-112425) (#112440)

gh-112414: Fix `AttributeError` when calling `repr()` on a namespace package imported with a custom loader (GH-112425)
(cherry picked from commit 0622839cfedacbb48eba27180fd0f0586fe97771)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>