pyupgrade --py36-plus **/*.py

[cclauss]

https://github.com/asottile/pyupgrade plus blacken two test files and add mypy in allow_failures mode.

[codecov-io]

Codecov Report

Merging #365 (c6d82e1) into master (b5468d9) will increase coverage by 0.04%.
The diff coverage is 21.05%.

@@            Coverage Diff             @@
##           master     #365      +/-   ##
==========================================
+ Coverage   30.38%   30.43%   +0.04%     
==========================================
  Files          39       39              
  Lines        1277     1275       -2     
==========================================
  Hits          388      388              
+ Misses        889      887       -2     

Impacted Files	Coverage Δ
patterns/behavioral/iterator.py	0.00% <0.00%> (ø)
patterns/behavioral/memento.py	0.00% <0.00%> (ø)
patterns/behavioral/publish_subscribe.py	91.17% <0.00%> (ø)
patterns/behavioral/template.py	0.00% <0.00%> (ø)
patterns/dependency_injection.py	0.00% <0.00%> (ø)
patterns/structural/bridge.py	80.00% <0.00%> (ø)
patterns/structural/facade.py	0.00% <0.00%> (ø)
patterns/structural/flyweight.py	0.00% <0.00%> (ø)
patterns/structural/mvc.py	0.00% <0.00%> (ø)
patterns/creational/abstract_factory.py	72.00% <100.00%> (ø)
... and 1 more

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