patch: branch source does not exist

[Martin Pool]

On 18/10/05, Robey Pointer <robey at lag.net> wrote:
> Sorry to keep sending little tiny patches.  This one fixes an error
> message when the source branch ("bzr branch /not/real") doesn't
> exist.  It's probably obvious from the patch. :)

I think I just fixed this in a different way.  Thanks for the patch though.

The standard approach from now on should be not to put a message in
the exception constructor, but rather to raise an exception whose
class corresponds to the situation.  So here for example we get
NotBranchError raised from inside Branch.open().

--
Martin