I believe I am experiencing the same bug:

Sorry, an error occurred in Snapcraft:
Traceback (most recent call last):
  File "/usr/bin/snapcraft", line 11, in <module>
    load_entry_point('snapcraft==2.43.1+18.4', 'console_scripts', 'snapcraft')()
  File "/usr/lib/python3/dist-packages/click/core.py", line 722, in __call__
    return self.main(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/click/core.py", line 697, in main
    rv = self.invoke(ctx)
  File "/usr/lib/python3/dist-packages/click/core.py", line 1043, in invoke
    return Command.invoke(self, ctx)
  File "/usr/lib/python3/dist-packages/click/core.py", line 895, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/lib/python3/dist-packages/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/usr/lib/python3/dist-packages/snapcraft/cli/_runner.py", line 93, in run
    ctx.forward(lifecyclecli.commands["snap"])
  File "/usr/lib/python3/dist-packages/click/core.py", line 553, in forward
    return self.invoke(cmd, **kwargs)
  File "/usr/lib/python3/dist-packages/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/snapcraft/cli/lifecycle.py", line 136, in snap
    project = _execute(steps.PRIME, parts=[], **kwargs)
  File "/usr/lib/python3/dist-packages/snapcraft/cli/lifecycle.py", line 30, in _execute
    project = get_project(**kwargs)
  File "/usr/lib/python3/dist-packages/snapcraft/cli/_options.py", line 68, in get_project
    snapcraft_yaml_file_path=snapcraft_yaml_file_path,
  File "/usr/lib/python3/dist-packages/snapcraft/project/_project.py", line 48, in __init__
    self.info = ProjectInfo(snapcraft_yaml_file_path=snapcraft_yaml_file_path)
  File "/usr/lib/python3/dist-packages/snapcraft/project/_project_info.py", line 32, in __init__
    self.__raw_snapcraft = _load_yaml(yaml_file_path=snapcraft_yaml_file_path)
  File "/usr/lib/python3/dist-packages/snapcraft/project/_project_info.py", line 65, in _load_yaml
    yaml_contents = yaml.safe_load(fp)  # type: ignore
  File "/usr/lib/python3/dist-packages/yaml/__init__.py", line 94, in safe_load
    return load(stream, SafeLoader)
  File "/usr/lib/python3/dist-packages/yaml/__init__.py", line 72, in load
    return loader.get_single_data()
  File "/usr/lib/python3/dist-packages/yaml/constructor.py", line 35, in get_single_data
    node = self.get_single_node()
  File "/usr/lib/python3/dist-packages/yaml/composer.py", line 36, in get_single_node
    document = self.compose_document()
  File "/usr/lib/python3/dist-packages/yaml/composer.py", line 55, in compose_document
    node = self.compose_node(None, None)
  File "/usr/lib/python3/dist-packages/yaml/composer.py", line 84, in compose_node
    node = self.compose_mapping_node(anchor)
  File "/usr/lib/python3/dist-packages/yaml/composer.py", line 133, in compose_mapping_node
    item_value = self.compose_node(node, item_key)
  File "/usr/lib/python3/dist-packages/yaml/composer.py", line 84, in compose_node
    node = self.compose_mapping_node(anchor)
  File "/usr/lib/python3/dist-packages/yaml/composer.py", line 127, in compose_mapping_node
    while not self.check_event(MappingEndEvent):
  File "/usr/lib/python3/dist-packages/yaml/parser.py", line 98, in check_event
    self.current_event = self.state()
  File "/usr/lib/python3/dist-packages/yaml/parser.py", line 439, in parse_block_mapping_key
    "expected <block end>, but found %r" % token.id, token.start_mark)
yaml.parser.ParserError: while parsing a block mapping
  in "snap/snapcraft.yaml", line 18, column 3
expected <block end>, but found '<block mapping start>'
  in "snap/snapcraft.yaml", line 21, column 5

snapcraft.yaml

name: crypto-test # you probably want to 'snapcraft register <name>'
version: '0.1' # just for humans, typically '1.2+git' or '1.3.2'
summary: Single-line elevator pitch for your amazing snap # 79 char long summary
description: |
  This is my-snap's description. You have a paragraph or two to tell the
  most important story about your snap. Keep it under 100 words though,
  we live in tweetspace and your description wants to look good in the snap
  store.

grade: devel # must be 'stable' to release into candidate/stable channels
confinement: devmode # use 'strict' once you have the right plugs and slots

apps:
    willards-crypto-test:
        command: willards-crypto-test

parts:
  crypto-test:
    source ../crypto_test.py
    # See 'snapcraft plugins'
    plugin: python
    python-version: 'python3'
    python-packages:
        - cryptoauthlib