Drop Python 2 Support

Python 2 is deprecated as of 2020. Dropping Python 2 support would simplify virtually every future change, since it invariably causes annoying and tricky-to-fix problems. Just one example is in my work on #81. Tests pass on Python 3 and fail on Python 2.

Todo

• Remove imports future, backports, pathlib2
• Update CI config
• Update dependencies in setup.py
• Remove monkey patch header_encode_patched
• Replace u"" with ""
• Remove coding=utf-8 from all files
• Remove code from tests that accounts for newline differences produced by the email library in Python 2 vs. 3
• Recursively search for “python 2”
• Recursively search for “utf.?8”
• Remove “inherit from object” and update pylint directives
• Update Contributing docs
• Bump major version before release

[awdeorio]

Edit: Maybe also update the README for users whose default Python path still points to Python 2? (Like users who set up on older versions of MacOS? I don’t actually know if it’s still bundled in newer versions.)

Brainwave! I think that adding this to the setup.py should do the trick:

    python_requires='>=3.4',

[seshrs]

Edit: Maybe also update the README for users whose default Python path still points to Python 2? (Like users who set up on older versions of MacOS? I don’t actually know if it’s still bundled in newer versions.)