Deprecate Python 2.7 and Python 3.5

[jadchaar]

Python 2.7 & 3.5 Deprecation Checklist

• [x] Update setup.py classifiers and python_requires to declare arrow only supports Python 3.6+
• [x] Drop Python < 3.6 from CI
• [x] Remove Python < 3.6 from Makefile
• [x] Run pyupgrade --py36-plus
• [x] Convert all formatting to f-strings (should be done by pyupgrade)
• [x] Remove all future imports
• [x] Remove any remaining python 2 import shadowing
• [x] Audit and overhaul requirements file
• [x] Change timestamp formatting to use datetime.timestamp()
• [x] Update timestamp calls in formatter.py
• [x] Replace hardcoded MAX_TIMESTAMP constant with datetime.max.timestamp()
• [x] Convert isinstance(value, numbers.Integral) to isinstance(value, int)
• [x] Remove isstr function
• [x] Remove __cmp__() method in arrow.py
• [x] Remove coverage pragmas and skipped tests for py27
• [x] Revisit enfold calls in code @systemcatch

Breaking changes for v1.0.0

• [x] Change timestamp from property to method in arrow.py (requires deprecation warning beforehand)
• [x] Change the return value of Arrow's timestamp method (currently a property) to a float

General Changes for v1.0.0

• [x] Remove beta label from setup.py

Closes: https://github.com/arrow-py/arrow/issues/465 Closes: https://github.com/arrow-py/arrow/issues/861 Closes: https://github.com/arrow-py/arrow/issues/739

[codecov[bot]]

Codecov Report

Merging #877 (6fc80d9) into master (609b630) will not change coverage. The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #877   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            9         9           
  Lines         1810      1796   -14     
  Branches       312       313    +1     
=========================================
- Hits          1810      1796   -14     

Impacted Files	Coverage Δ
arrow/api.py	100.00% <ø> (ø)
arrow/arrow.py	100.00% <100.00%> (ø)
arrow/constants.py	100.00% <100.00%> (ø)
arrow/factory.py	100.00% <100.00%> (ø)
arrow/formatter.py	100.00% <100.00%> (ø)
arrow/locales.py	100.00% <100.00%> (ø)
arrow/parser.py	100.00% <100.00%> (ø)
arrow/util.py	100.00% <100.00%> (ø)

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[jadchaar]

Should be ready for review @systemcatch @krisfremen. All what remains is updating the enfold calls, which @systemcatch is more familiar with.

[jadchaar]

Thanks for the feedback. We had a note to revisit enfold in the copy constructor since we would now be able to just copy the datetime object as is rather than having to enfold again. Do we want to ignore that and just leave it for a future PR?

[systemcatch]

Thanks for the feedback. We had a note to revisit enfold in the copy constructor since we would now be able to just copy the datetime object as is rather than having to enfold again. Do we want to ignore that and just leave it for a future PR?

Not sure what you mean by copy constructor?

[jadchaar]

Oh oops sorry I meant replace: https://github.com/arrow-py/arrow/blob/609b630b9f5a4b814377053965b93d78fd979c64/arrow/arrow.py#L777-L823

We probably don't need enfold here anymore since datetime would replace fold natively. Thoughts?

[systemcatch]

You're right, how about I make an issue to update the enfold calls after 1.0.0 is released?

[jadchaar]

Ref: https://github.com/arrow-py/arrow/issues/878

Want to approve so we can get this merged @systemcatch?

[jadchaar]

@isac322 You should be good to now implement type checking off of master!