Bump pyflakes from 1.6.0 to 2.1.0

[dependabot-preview]

Bumps pyflakes from 1.6.0 to 2.1.0.

Changelog

Sourced from pyflakes's changelog.

2.1.0 (2019-01-23)

• Allow intentional assignment to variables named _
• Recognize __module__ as a valid name in class scope
• pyflakes.checker.Checker supports checking of partial ast trees
• Detect assign-before-use for local variables which shadow builtin names
• Detect invalid print syntax using >> operator
• Treat async for the same as a for loop for introducing variables
• Add detection for list concatenation in __all__
• Exempt [**typing**](https://github.com/typing).overload from duplicate function declaration
• Importing a submodule of an as-aliased import-import is marked as
  used
• Report undefined names from __all__ as possibly coming from a *
  import
• Add support for changes in Python 3.8-dev
• Add support for PEP 563 (from __future__ import annotations)
• Include Python version and platform information in pyflakes --version
• Recognize __annotations__ as a valid magic global in Python 3.6+
• Mark names used in PEP 484 # type: ... comments as used
• Add check for use of is operator with str, bytes, and int
  literals

2.0.0 (2018-05-20)

• Drop support for EOL Python <2.7 and 3.2-3.3
• Check for unused exception binding in except: block
• Handle string literal type annotations
• Ignore redefinitions of _, unless originally defined by import
• Support __class__ without self in Python 3
• Issue an error for raise NotImplemented(...)

Commits

• 4bc1f21 Write changelog and bump version for 2.1.0
• 65fdfad Fix regression with __all__ = [not, strings]
• 14f28ba Use file_tokens to better match flake8 api
• 357a2e3 Allow star args in type comments
• 7272b10 Add check for use of 'is' operator with str, bytes, and int literals
• 1f58890 Set the proper scope for async def
• 1f4e377 Fix python3.8 docstring offsets
• f144487 Move type annotations tests to their own class
• ac0aeba Parse PEP 484 type comments
• 009f4e7 Update TravisCI to use flake8 3.6.0 (#398)
• Additional commits viewable in compare view

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[codecov]

Codecov Report

Merging #20 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master    #20   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           5      5           
  Lines          52     52           
=====================================
  Hits           52     52

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[dependabot-preview]

Superseded by #27.