Transport error: Server refuses to fullfil the request

[Ben Finney]

Howdy all,

I'm trying to branch from a public branch, but it's failing partway
through with the following message:

=====
bzr> version
Bazaar (bzr) 1.3.1
  Python interpreter: /usr/bin/python 2.5.2.final.0
  Python standard library: /usr/lib/python2.5
  bzrlib: /usr/lib/python2.5/site-packages/bzrlib
  Bazaar configuration: /home/bignose/.bazaar
  Bazaar log file: /home/bignose/.bzr.log
[...]

bzr> info http://people.debian.org/~mvo/bzr/python-apt/python-apt--debian-sid/
Standalone branch (format: dirstate or knit)
Location:
  branch root: http://people.debian.org/%7Emvo/bzr/python-apt/python-apt--debian-sid/

bzr> branch http://people.debian.org/~mvo/bzr/python-apt/python-apt--debian-sid/
Working tree format 3 is deprecated and a better format is available.
It is recommended that you upgrade by running the command
  bzr upgrade http://people.debian.org/%7Emvo/bzr/python-apt/python-apt--debian-sid/
Transport error: Server refuses to fullfil the request
=====

What can I do to get a branch from this one?