warn if host not found when trying to contact bound branch

[Jamie Wilkinson]

Hey,

I just tried to pull from a mirror of a branch, because I left my laptop at
home today and I know that it's up to date with an http mirror that I push
out to, so I tried to pull from that mirror URL into my branch at work.

It kept saying "ssh: connect to host dawn port 22: No route to host" and it
took me a couple of attempts before I realised that I had bound the branch
to my laptop.

Would it be possible to put the reason for the connection attempt in the
exception?

I.e., rather than juyst say:

booty% bzr pull http://repo.spacepants.org/z/z.dev
/ [                                                            ] Pull phase
0/2ssh: connect to host dawn port 22: No route to host
bzr: ERROR: exceptions.EOFError:
  at /usr/lib/python2.4/site-packages/paramiko/sftp.py line 147
  in _read_all

it could note:

ssh: connect to host dawn port 22: No route to host
bzr: ERROR: exceptions.EOFError:
 ...
attempting to contact dawn before repo.spacpeants.org because branch is
bound.

or something to that effect, as a friendly reminder that one might need to
unbind before working in this branch.

Thanks.