Remove classifier for Python 3.4 for end-of-life.

[crwilcox]

Python 3.4 has reached EOL. https://www.python.org/dev/peps/pep-0429/

At this point we should remove the classifier for 3.4 and discourage its use. This change doesn't prevent users from installing this library on 3.4. Doing so would require rev-ing versions of our libraries and create a good deal of noise. My suggestion is that we modify python_requires as other breaking changes come, removing 3.4 at that point.

[tseaver]

@crwilcox

My suggestion is that we modify python_requires as other breaking changes come, removing 3.4 at that point.

We aren't likely to make changes which break 3.4 before we also drop 2.7 support:

• New syntax is obviously problematic (e.g. we've already told folks that async / await redesign efforts are blocked by 2.7 compat).
• New library stuff likewise (minimal in 3.5, and again blocked by 2.7 compat).

See: https://docs.python.org/3/whatsnew/3.5.html

[crwilcox]

@tseaver we are 100% on the same page on this one. If we batch it with 2.7 it will save a major bump and be less disruptive.