brz revert fails

I did a brz pull, and it pulled the repo, but then hit an error (which I failed to save). It failed to update the actual files (but I can still branch from it successfully, so the repo is updated).

Now when I try to brz revert to get the working tree to update, I get this error:

> brz revert
brz: ERROR: StopIteration:

Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/breezy/commands.py", line 1016, in exception_to_return_code
    return the_callable(*args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/breezy/commands.py", line 1202, in run_bzr
    ret = run(*run_argv)
  File "/usr/local/lib/python3.7/site-packages/breezy/commands.py", line 759, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/usr/local/lib/python3.7/site-packages/breezy/commands.py", line 784, in run
    return self._operation.run_simple(*args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/breezy/cleanup.py", line 137, in run_simple
    self.cleanups, self.func, *args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/breezy/cleanup.py", line 166, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/breezy/builtins.py", line 4854, in run
    self._revert_tree_to_revision(tree, revision, file_list, no_backup)
  File "/usr/local/lib/python3.7/site-packages/breezy/builtins.py", line 4860, in _revert_tree_to_revision
    report_changes=True)
  File "/usr/local/lib/python3.7/site-packages/breezy/workingtree.py", line 1048, in revert
    report_changes)
  File "/usr/local/lib/python3.7/site-packages/breezy/transform.py", line 2861, in revert
    delta.report_changes(tt.iter_changes(), change_reporter)
  File "/usr/local/lib/python3.7/site-packages/breezy/transform.py", line 988, in iter_changes
    self._from_file_data(from_trans_id, from_versioned, from_path)
  File "/usr/local/lib/python3.7/site-packages/breezy/transform.py", line 909, in _from_file_data
    specific_files=[from_path]))[1]
StopIteration

brz 3.0.1 on python 3.7.4 (Darwin-18.7.0-x86_64-i386-64bit)
arguments: ['/usr/local/bin/brz', 'revert']
plugins: bash_completion[3.0.1], changelog_merge[3.0.1],
    commitfromnews[unknown], cvs[3.0.1], darcs[unknown], email[unknown],
    fastimport[unknown], launchpad[3.0.1], mtn[3.0.1],
    netrc_credential_store[3.0.1], news_merge[3.0.1], po_merge[3.0.1],
    propose[unknown], repodebug[unknown], stats[3.0.1], upload[3.0.1],
    weave_fmt[3.0.1]
encoding: 'utf-8', fsenc: 'utf-8', lang: 'en_GB.UTF-8'