There are three significant changes here:
- rewrite ring.ErrDifferentSeeds errors
- remove the pre-checking of ranges and instead rewrite
ring.ErrDifferentRange errors
- don't pruneNicknames() and signal ringUpdated() when there was an
error
We don't rewrite other errors since our current belief is that only
ErrDifferentSeeds and ErrDifferentRange can arise from user error.