Update pyflakes to 2.1.1

[pyup-bot]

This PR updates pyflakes from 2.0.0 to 2.1.1.

Changelog

2.1.0

- 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.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

Links

• PyPI: https://pypi.org/project/pyflakes
• Changelog: https://pyup.io/changelogs/pyflakes/
• Repo: https://github.com/PyCQA/pyflakes

[coveralls]

Coverage remained the same at 100.0% when pulling 6a20808 on pyup-update-pyflakes-2.0.0-to-2.1.1 into ea4ce24 on master.

[pyup-bot]

Closing this in favor of #309