Non-Subversion branch gives "svn.core.SubversionException"

[Ben Finney]

Howdy all,

When I try to branch from a particular URL, it fails with the error
"svn.core.SubversionException" even though the branch has nothing to
do with Subversion.

=====
$ bzr branch http://vcs.whitetree.org/bzr/public/gracie/gracie.debian/
bzr: ERROR: svn.core.SubversionException: ("Repository moved permanently to 'http://vcs.whitetree.org/bzr/public/gracie/'; please relocate", 175011)

Traceback (most recent call last):
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 846, in run_bzr_catch_errors
    return run_bzr(argv)
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 797, in run_bzr
    ret = run(*run_argv)
  File "/usr/lib/python2.5/site-packages/bzrlib/commands.py", line 499, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/usr/lib/python2.5/site-packages/bzrlib/builtins.py", line 916, in run
    from_location)
  File "/usr/lib/python2.5/site-packages/bzrlib/bzrdir.py", line 790, in open_tree_or_branch
    return bzrdir._get_tree_branch()
  File "/usr/lib/python2.5/site-packages/bzrlib/bzrdir.py", line 775, in _get_tree_branch
    branch = self.open_branch()
  File "/usr/lib/python2.5/site-packages/bzrlib/bzrdir.py", line 1371, in open_branch
    return format.open(self, _found=True)
  File "/usr/lib/python2.5/site-packages/bzrlib/branch.py", line 1213, in open
    _repository=a_bzrdir.find_repository())
  File "/usr/lib/python2.5/site-packages/bzrlib/bzrdir.py", line 559, in find_repository
    found_repo = self._find_containing(usable_repository)
  File "/usr/lib/python2.5/site-packages/bzrlib/bzrdir.py", line 535, in _find_containing
    next_transport)[0]
  File "/usr/lib/python2.5/site-packages/bzrlib/bzrdir.py", line 750, in open_containing_from_transport
    result = BzrDir.open_from_transport(a_transport)
  File "/usr/lib/python2.5/site-packages/bzrlib/bzrdir.py", line 709, in open_from_transport
    return format.open(transport, _found=True)
  File "/usr/lib/python2.5/site-packages/bzrlib/bzrdir.py", line 1572, in open
    return self._open(transport)
  File "/usr/lib/python2.5/site-packages/bzrlib/plugins/svn/format.py", line 70, in _open
    return remote.SvnRemoteAccess(transport, self)
  File "/usr/lib/python2.5/site-packages/bzrlib/plugins/svn/remote.py", line 41, in __init__
    _transport = get_svn_ra_transport(_transport)
  File "/usr/lib/python2.5/site-packages/bzrlib/plugins/svn/transport.py", line 59, in get_svn_ra_transport
    return SvnRaTransport(bzr_transport.base)
  File "/usr/lib/python2.5/site-packages/bzrlib/plugins/svn/errors.py", line 107, in convert
    raise convert_error(e)
SubversionException: ("Repository moved permanently to 'http://vcs.whitetree.org/bzr/public/gracie/'; please relocate", 175011)

bzr 1.5 on python 2.5.2 (linux2)
arguments: ['/usr/bin/bzr', 'branch', 'http://vcs.whitetree.org/bzr/public/gracie/gracie.debian/']
encoding: 'UTF-8', fsenc: 'UTF-8', lang: 'en_AU.UTF-8'
plugins:
  builddeb             /usr/lib/python2.5/site-packages/bzrlib/plugins/builddeb [0.95.0dev0]
  bzrtools             /usr/lib/python2.5/site-packages/bzrlib/plugins/bzrtools [1.5.0]
  cia                  /usr/lib/python2.5/site-packages/bzrlib/plugins/cia [unknown]
  email                /usr/lib/python2.5/site-packages/bzrlib/plugins/email [unknown]
  launchpad            /usr/lib/python2.5/site-packages/bzrlib/plugins/launchpad [unknown]
  loom                 /usr/lib/python2.5/site-packages/bzrlib/plugins/loom [1.4.0dev0]
  pqm                  /usr/lib/python2.5/site-packages/bzrlib/plugins/pqm [1.0.0dev0]
  svn                  /usr/lib/python2.5/site-packages/bzrlib/plugins/svn [0.4.10]
*** Bazaar has encountered an internal error.
    Please report a bug at https://bugs.launchpad.net/bzr/+filebug
    including this traceback, and a description of what you
    were doing when the error occurred.
=====

What's causing this strange result? How can I branch from this URL?

-- 
 \     “No matter how far down the wrong road you've gone, turn back.” |
  `\                                                  —Turkish proverb |
_o__)                                                                  |
Ben Finney