Comment 8 for bug 1518150

With a code point U+20021

We get
Traceback (most recent call last):
  File "/usr/bin/snapcraft", line 33, in <module>
    snapcraft.main.main()
  File "/usr/lib/python3/dist-packages/snapcraft/main.py", line 148, in main
    args.func(args)
  File "/usr/lib/python3/dist-packages/snapcraft/cmds.py", line 98, in assemble
    snap(args)
  File "/usr/lib/python3/dist-packages/snapcraft/cmds.py", line 79, in snap
    cmd(args)
  File "/usr/lib/python3/dist-packages/snapcraft/cmds.py", line 307, in cmd
    config = _load_config()
  File "/usr/lib/python3/dist-packages/snapcraft/cmds.py", line 373, in _load_config
    _config = snapcraft.yaml.Config()
  File "/usr/lib/python3/dist-packages/snapcraft/yaml.py", line 98, in __init__
    self.data = _snapcraft_yaml_load()
  File "/usr/lib/python3/dist-packages/snapcraft/yaml.py", line 324, in _snapcraft_yaml_load
    return yaml.load(fp)
  File "/usr/lib/python3/dist-packages/yaml/__init__.py", line 70, in load
    loader = Loader(stream)
  File "/usr/lib/python3/dist-packages/yaml/loader.py", line 34, in __init__
    Reader.__init__(self, stream)
  File "/usr/lib/python3/dist-packages/yaml/reader.py", line 85, in __init__
    self.determine_encoding()
  File "/usr/lib/python3/dist-packages/yaml/reader.py", line 135, in determine_encoding
    self.update(1)
  File "/usr/lib/python3/dist-packages/yaml/reader.py", line 169, in update
    self.check_printable(data)
  File "/usr/lib/python3/dist-packages/yaml/reader.py", line 144, in check_printable
    'unicode', "special characters are not allowed")
yaml.reader.ReaderError: unacceptable character #x20021: special characters are not allowed
  in "snapcraft.yaml", position 96