[MERGE][#230902][1.8] Fix “Must end write group ...” error due to error raised in a finally block

[Andrew Bennetts]

Hi Martin,

Martin Pool wrote:
> Martin Pool has voted tweak.
> Status is now: Conditionally approved
> Comment:
> After some discussion I believe it would be better for unlock to warn  
> but not propagate an error encountered while unlocking.  But this patch  
> is ok with me to merge to 1.8.
>
> It needs a news file though.

A branch for 1.8 with the NEWS file addition is at
<http://people.ubuntu.com/~andrew/bzr/push-unlock-1.8>.  I'd merge it to 1.8
myself, but apparently I don't have sufficent rights in PQM.

-Andrew.