Missing __iter__ on ResponseFile during import-dsc

gwenhwyvar:~/src/subunit/unstable% BZR_PDB=1 ~/src/bzr/bzr.dev/bzr import-dsc -F foo
bzr: ERROR: exceptions.TypeError: 'ResponseFile' object is not iterable

Traceback (most recent call last):
  File "/home/jelmer/src/bzr/bzr.dev/bzrlib/commands.py", line 930, in exception_to_return_code
    return the_callable(*args, **kwargs)
  File "/home/jelmer/src/bzr/bzr.dev/bzrlib/commands.py", line 1121, in run_bzr
    ret = run(*run_argv)
  File "/home/jelmer/src/bzr/bzr.dev/bzrlib/commands.py", line 673, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/home/jelmer/src/bzr/bzr.dev/bzrlib/commands.py", line 697, in run
    return self._operation.run_simple(*args, **kwargs)
  File "/home/jelmer/src/bzr/bzr.dev/bzrlib/cleanup.py", line 136, in run_simple
    self.cleanups, self.func, *args, **kwargs)
  File "/home/jelmer/src/bzr/bzr.dev/bzrlib/cleanup.py", line 166, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/plugins/builddeb/cmds.py", line 1002, in run
    self.import_many(db, files_list, orig_target)
  File "/usr/lib/python2.7/dist-packages/bzrlib/plugins/builddeb/cmds.py", line 911, in import_many
    files_list.sort(cmp=DscComp(cache).cmp)
  File "/usr/lib/python2.7/dist-packages/bzrlib/plugins/builddeb/import_dsc.py", line 121, in cmp
    dsc1 = self.cache.get_dsc(dscname1)
  File "/usr/lib/python2.7/dist-packages/bzrlib/plugins/builddeb/import_dsc.py", line 103, in get_dsc
    dsc1 = deb822.Dsc(f1)
  File "/usr/lib/python2.7/dist-packages/debian/deb822.py", line 1149, in __init__
    self.split_gpg_and_payload(sequence)
  File "/usr/lib/python2.7/dist-packages/debian/deb822.py", line 631, in split_gpg_and_payload
    for line in sequence:
TypeError: 'ResponseFile' object is not iterable

bzr 2.6.0dev3 on python 2.7.5 (Linux-3.8-2-amd64-x86_64-with-debian-jessie-
    sid)
arguments: ['/home/jelmer/src/bzr/bzr.dev/bzr', 'import-dsc', '-F', 'foo']
plugins: bash_completion[2.6.0dev3], builddeb[2.7.0dev],
    changelog_merge[2.6.0dev3], git[0.6.9], grep[2.6.0dev3],
    launchpad[2.6.0dev3], netrc_credential_store[2.6.0dev3],
    news_merge[2.6.0dev3], po_merge[2.6.0dev3], weave_fmt[2.6.0dev3]
encoding: 'utf-8', fsenc: 'UTF-8', lang: 'en_GB.UTF-8'

*** Bazaar has encountered an internal error. This probably indicates a
    bug in Bazaar. You can help us fix it by filing a bug report at
        https://bugs.launchpad.net/bzr/+filebug
    including this traceback and a description of the problem.
**** entering debugger