typing: correct the signature of error.CommandError There's a place in `mercurial.dispatch._parse()` that passes None if a parse error happens before the command can be parsed out, and casting the error to bytes works fine because the command and message fields are apparently ignored. Likewise, TortoiseHg similarly passes None for the same reason.

[build-system]
requires = ["setuptools", "wheel"]

[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
'''
skip-string-normalization = true
quiet = true