register-branch --author without email address

register-branch with an --author argument that doesn't contain an '@'
causes a confusing error:

bzr: ERROR: xmlrpclib.Fault: <Fault -1: 'Unexpected Zope exception: AssertionError: argument must be tuple or Fault instance'>

Traceback (most recent call last):
  File "/usr/lib/python2.4/site-packages/bzrlib/commands.py", line 694, in run_bzr_catch_errors
    return run_bzr(argv)
  File "/usr/lib/python2.4/site-packages/bzrlib/commands.py", line 656, in run_bzr
    ret = run(*run_argv)
  File "/usr/lib/python2.4/site-packages/bzrlib/commands.py", line 281, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/usr/lib/python2.4/site-packages/bzrlib/plugins/launchpad/__init__.py", line 111, in run
    branch_object_url = rego.submit(service)
  File "/usr/lib/python2.4/site-packages/bzrlib/plugins/launchpad/lp_registration.py", line 140, in submit
    return service.send_request(self._methodname, self._request_params())
  File "/usr/lib/python2.4/site-packages/bzrlib/plugins/launchpad/lp_registration.py", line 107, in send_request
    result = method(*method_params)
  File "/usr/lib/python2.4/xmlrpclib.py", line 1096, in __call__
    return self.__send(self.__name, args)
  File "/usr/lib/python2.4/xmlrpclib.py", line 1383, in __request
    verbose=self.__verbose
  File "/usr/lib/python2.4/xmlrpclib.py", line 1147, in request
    return self._parse_response(h.getfile(), sock)
  File "/usr/lib/python2.4/xmlrpclib.py", line 1286, in _parse_response
    return u.close()
  File "/usr/lib/python2.4/xmlrpclib.py", line 744, in close
    raise Fault(**self._stack[0])
Fault: <Fault -1: 'Unexpected Zope exception: AssertionError: argument must be tuple or Fault instance'>

bzr 0.9.0dev0 on python 2.4.4.candidate.0 (linux2)

It should say something more user-friendly instead.