_hermes_repo_root used parents[1] which resolves to tools/ instead of
the repository root. The file lives at tools/environments/local.py so it
needs parents[2] to reach the actual repo root that Electron injects
into PYTHONPATH.
The test test_repo_root_stripped reused the module constant under test
as its input. This made it pass regardless of what the constant pointed
at. The test now computes the real repo root independently from the
source file location. It fails with the old parents[1] code and passes
with the fix.
Reported by spfcraze in PR #78917 review.
Yiipu
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