sshpeer: add a method to check if a doublepipe is closed So we can tell in a next commit if we're trying to close an already closed connection or not (in which case, we may warn). Differential Revision: https://phab.mercurial-scm.org/D9996

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