When asking to release to a branch that's too long, a traceback is printed that gives no hints as to the source of the error.

(I think it's looking for an 'errors' key in the response that isn't there)

$ snapcraft release interdenominational-counterintelligences 1 'stable/It-was-the-best-of-times--it-was-the-worst-of-times--it-was-the-age-of-wisdom--it-was-the-age-of-foolishness--it-was-the-epoch-of-belief--it-was-the-epoch-of-incredulity--it-was-the-season-of-Light--it-was-the-season-of-Darkness--it-was-the-spring-of-hope--it-was-the-winter-of-despair'
Traceback (most recent call last):
  File "/snap/snapcraft/1094/bin/snapcraft", line 11, in <module>
    load_entry_point('snapcraft==2.39', 'console_scripts', 'snapcraft')()
  File "/snap/snapcraft/1094/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 565, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File "/snap/snapcraft/1094/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2631, in load_entry_point
    return ep.load()
  File "/snap/snapcraft/1094/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2291, in load
    return self.resolve()
  File "/snap/snapcraft/1094/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2297, in resolve
    module = __import__(self.module_name, fromlist=['__name__'], level=0)
  File "/snap/snapcraft/1094/lib/python3.6/site-packages/snapcraft/cli/__main__.py", line 43, in <module>
    run(prog_name='snapcraft')
  File "/snap/snapcraft/1094/lib/python3.6/site-packages/click/core.py", line 722, in __call__
    return self.main(*args, **kwargs)
  File "/snap/snapcraft/1094/lib/python3.6/site-packages/click/core.py", line 697, in main
    rv = self.invoke(ctx)
  File "/snap/snapcraft/1094/lib/python3.6/site-packages/click/core.py", line 1066, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/snap/snapcraft/1094/lib/python3.6/site-packages/click/core.py", line 895, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/snap/snapcraft/1094/lib/python3.6/site-packages/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/snap/snapcraft/1094/lib/python3.6/site-packages/snapcraft/cli/store.py", line 210, in release
    snapcraft.release(snap_name, revision, channels.split(','))
  File "/snap/snapcraft/1094/lib/python3.6/site-packages/snapcraft/_store.py", line 607, in release
    channels = store.release(snap_name, revision, release_channels)
  File "/snap/snapcraft/1094/lib/python3.6/site-packages/snapcraft/storeapi/_store_client.py", line 156, in release
    self.sca.snap_release, snap_name, revision, channels)
  File "/snap/snapcraft/1094/lib/python3.6/site-packages/snapcraft/storeapi/_store_client.py", line 78, in _refresh_if_necessary
    return func(*args, **kwargs)
  File "/snap/snapcraft/1094/lib/python3.6/site-packages/snapcraft/storeapi/_sca_client.py", line 176, in snap_release
    raise errors.StoreReleaseError(data['name'], response)
  File "/snap/snapcraft/1094/lib/python3.6/site-packages/snapcraft/storeapi/errors.py", line 353, in __init__
    self.fmt = fmt_error(response)
  File "/snap/snapcraft/1094/lib/python3.6/site-packages/snapcraft/storeapi/errors.py", line 395, in __fmt_error_unknown
    fmt = '{errors}'.format(**response_json)
KeyError: 'errors'