Drop support EOL Pythons

Python 2.7 and 3.4, and 3.5 are end of life. They are no longer receiving bug fixes, including for security issues.

For a list of supported and EOL Pythons, see:

Supported: https://devguide.python.org/#status-of-python-branches EOL: https://devguide.python.org/devcycle/#end-of-life-branches

Removing support for EOL Pythons will reduce testing and maintenance resources while allowing the library to move towards a modern Python 3 style.

Next steps

• Do one additional release that supports Python 2.7 to include recent changes
• Create a “1.x” or “python2.7-support” branch to allow ongoing Python 2 maintenance
• Bump the major version number on the master branch (not necessary)
• Review and merge PR #281
• Do another release for Python 3+

[hartwork]

Regrading the major version bump: Personally I don’t think a bump in major version is needed or even helpful because it signals breaking changes (a la semver) to the users of alive Python versions (who don’t need any signal) while it doesn’t signal anything to user of end-of-life versions of Python (due to proper python_requires). I get the idea but I think the details work against the intent. What do you think?

[jdufresne]

Before this we’ll have to create one last release though.

I think we’re in a good position do this. @sethmlarson would you like to go ahead?