New top-level package: wrench

This tiny package provides simple way for any part of Juju to check if a "wrench should be dropped in the works" at some part of Juju's execution. It checks $datadir/wrench for files which signal that something should break, performing some error checking and logging.

The idea is that judicious calls to wrench.IsEnabled can be permanently left in the code to aid manual and CI testing.


please move the lock above the thing it locks, the common pattern is to do

lock sync.Mu // lock synchronises access to the following fields
thingA int
thingB bool

// more unrelated things