test-defaults.pkl contains the serialization of the manifest_defaults
dictionary. There are two formats:
- Paths of test manifests.
- Tuple (ancestor, path) for DEFAULT in included test manifests.
The tuple was introduced in bug 1498636, with ancestor being an absolute
path.
In bug 1600314, ancestor_manifest became a relative path. The reader
logic (in resolve.py) was updated to expect an absolute path, but the
writer logic was not special-cased, and therefore wrote a relative
path to `test-defaults.pkl` instead of an absolute path.
Due to these two being out of sync, the reader was unable to look up the
DEFAULT of included test manifests.
This patch updates the reader to expect a relative path in the tuple, to
fix the reported issue.
Differential Revision: https://phabricator.services.mozilla.com/D232906
ccd46db539