py3: use socket.makefile() instead of dropped smtplib.SSLFakeFile
The latter (undocumented internal) class got removed in Python 3.3. Use
socket.makefile() as suggested:
https://docs.python.org/3/whatsnew/3.3.html#porting-python-code
[tool.black]
line-length = 80
exclude = 'build/|wheelhouse/|dist/|packages/|\.hg/|\.mypy_cache/|\.venv/|mercurial/thirdparty/|hgext/fsmonitor/pywatchman/|contrib/python-zstandard/'