This case was complicated because someone had added new non-autogened test to an autogened file.  In particular, those new tests used two variables (%J and %j) which differeded only in capitalization.  The auto-updater doesn't distinguish case, so this meant auto-gened versions of the new tests failed with non-obvious errors.

There are two key lessons here:
1) Please don't use two values which differ only in case.  This is problematic for automatic tooling, but is also hard to understand for a human.
2) Please DO NOT add new tests to an autogened test without running autogen again.  If autogen doesn't pass on your new test, put them in a separate file.