A recent commit (r. 35764) by Campbell will break ShapeKey Drivers and/or ShapeKey Animation, as the "keys" collection in the "Key" ID-Blocks (i.e. container for ShapeKeys) has been renamed to "key_blocks", to avoid conflicts with Python's builtin datatypes.
Recommended Remediation Procedure:
Run the "FCurve/Driver Version Fix" operator from the Help menu.
- You will need a build of at least r.
Thank you for your attention.