re2: fix reporting of availability in `hg debuginstall`
We add and use an official API to check is re2 is available. This prevent the
bug previously in place were debuginstall was considering confusing `None`
(i.e. non-initialized) and `False` (i.e. unavailable).
[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