Remove support for end-of-life Python 2.7

[jdufresne]

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Description of change

Python 2.7 is end of life. It is no longer receiving bug fixes, including for security issues. Python 2.7 went EOL on 2020-01-01. For additional details on support Python versions, 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. Python 2.7 users can continue to use the previous version of redis-py.

Was able to simplify the code:

• Removed redis._compat module
• Removed future imports
• Removed object from class definition (all classes are new style)
• Removed long (Python 3 unified numeric types)
• Removed deprecated nonzero method
• Use simpler Python 3 super() syntax
• Use unified OSError exception
• Use yield from syntax

[andymccurdy]

Few PRs would make me happier to merge. I'm jealous that Django and other major Python packages have already made this change. Sadly, https://pypistats.org/packages/redis shows that Python 2 clients are downloading the redis-py package anywhere between 20% and 50% depending on the day. And I know some of the Redis Labs folks are still using Python 2 internally.

I think the best course of action is to pick a date in the future and announce that Python 2 will no longer be supported after that date. Perhaps July 1 2020? That gives everyone about 3 months to port or accept that they won't be getting any new features.

@itamarhaber @RoeyPrat thoughts?

[jdufresne]

Thanks @andymccurdy

That plans makes sense to me.

[codecov-io]

Codecov Report

Merging #1318 into master will increase coverage by 0.18%.
The diff coverage is 85.13%.

@@            Coverage Diff             @@
##           master    #1318      +/-   ##
==========================================
+ Coverage   92.87%   93.06%   +0.18%     
==========================================
  Files          20       19       -1     
  Lines        6543     6375     -168     
==========================================
- Hits         6077     5933     -144     
+ Misses        466      442      -24     

Impacted Files	Coverage Δ
redis/connection.py	82.99% <63.04%> (+0.66%)	⬆️
redis/client.py	86.10% <81.17%> (-0.17%)	⬇️
redis/lock.py	100.00% <100.00%> (ø)
redis/sentinel.py	83.68% <100.00%> (ø)
redis/utils.py	72.22% <100.00%> (+3.47%)	⬆️
tests/conftest.py	96.87% <100.00%> (ø)
tests/test_commands.py	99.94% <100.00%> (-0.01%)	⬇️
tests/test_connection.py	100.00% <100.00%> (ø)
tests/test_connection_pool.py	97.84% <100.00%> (ø)
tests/test_encoding.py	98.75% <100.00%> (+1.13%)	⬆️
... and 7 more

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[andymccurdy]

Announced today that Python 3.5.x will be the last release that supports Python 2. We'll support bug fixes and security patches in the 3.5.x line through the end of July 2020. redis-py 4.x (the next version) will be Python 3 only.

I'll merge this into master soon and we'll back port any bug fixes/security patches to the 3.5.0 branch.

[codecov-commenter]

Codecov Report

Merging #1318 into master will increase coverage by 0.02%.
The diff coverage is 77.55%.

@@            Coverage Diff             @@
##           master    #1318      +/-   ##
==========================================
+ Coverage   85.48%   85.50%   +0.02%     
==========================================
  Files           7        6       -1     
  Lines        3017     2863     -154     
==========================================
- Hits         2579     2448     -131     
+ Misses        438      415      -23     

Impacted Files	Coverage Δ
redis/connection.py	82.03% <63.04%> (+0.62%)	⬆️
redis/client.py	85.83% <81.17%> (-0.17%)	⬇️
redis/lock.py	100.00% <100.00%> (ø)
redis/sentinel.py	86.80% <100.00%> (ø)
redis/utils.py	72.22% <100.00%> (+3.47%)	⬆️

---

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