I don't understand launchpad very much, but the proposed fix from https://code.launchpad.net/~jelmer/brz/python3.8-1/+merge/374051 does not solve the original issue:

$ brz init-repo brz && cd brz && brz -Derror branch lp:brz brz.dev
Shared repository with trees (format: 2a)
Location:
  shared repository: brz
You have not informed bzr of your Launchpad ID, and you must do this to
write to Launchpad or access private data.  See "bzr help launchpad-login".
brz: ERROR: breezy.errors.BzrCommandError: The branch lp:brz has no revision None.                                                                                                                                              

Traceback (most recent call last):
  File "/usr/lib64/python3.8/site-packages/breezy/builtins.py", line 1513, in run
    to_dir = br_from.controldir.sprout(
  File "/usr/lib64/python3.8/site-packages/breezy/bzr/bzrdir.py", line 380, in sprout
    return operation.run(
  File "/usr/lib64/python3.8/site-packages/breezy/cleanup.py", line 132, in run
    return _do_with_cleanups(
  File "/usr/lib64/python3.8/site-packages/breezy/cleanup.py", line 166, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "/usr/lib64/python3.8/site-packages/breezy/bzr/bzrdir.py", line 435, in _sprout
    fetch_spec = fetch_spec_factory.make_fetch_spec()
  File "/usr/lib64/python3.8/site-packages/breezy/bzr/fetch.py", line 429, in make_fetch_spec
    return vf_search.NotInOtherForRevs(self.target_repo, self.source_repo,
  File "/usr/lib64/python3.8/site-packages/breezy/bzr/vf_search.py", line 375, in execute
    return self.to_repo.search_missing_revision_ids(
  File "/usr/lib64/python3.8/site-packages/breezy/repository.py", line 585, in search_missing_revision_ids
    return InterRepository.get(other, self).search_missing_revision_ids(
  File "/usr/lib64/python3.8/site-packages/breezy/bzr/vf_repository.py", line 2429, in search_missing_revision_ids
    result = self._walk_to_common_revisions(revision_ids,
  File "/usr/lib64/python3.8/site-packages/breezy/bzr/vf_repository.py", line 2396, in _walk_to_common_revisions
    raise errors.NoSuchRevision(
breezy.errors.NoSuchRevision: CHKInventoryRepository('http://bazaar.launchpad.net/~brz/brz/trunk/.bzr/repository/') has no revision <email address hidden>'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib64/python3.8/site-packages/breezy/commands.py", line 1016, in exception_to_return_code
    return the_callable(*args, **kwargs)
  File "/usr/lib64/python3.8/site-packages/breezy/commands.py", line 1202, in run_bzr
    ret = run(*run_argv)
  File "/usr/lib64/python3.8/site-packages/breezy/commands.py", line 759, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/usr/lib64/python3.8/site-packages/breezy/commands.py", line 784, in run
    return self._operation.run_simple(*args, **kwargs)
  File "/usr/lib64/python3.8/site-packages/breezy/cleanup.py", line 136, in run_simple
    return _do_with_cleanups(
  File "/usr/lib64/python3.8/site-packages/breezy/cleanup.py", line 166, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "/usr/lib64/python3.8/site-packages/breezy/builtins.py", line 1526, in run
    raise errors.BzrCommandError(msg)
breezy.errors.BzrCommandError: The branch lp:brz has no revision None.