Bump pyflakes from 2.1.1 to 2.2.0 (#29)

Bumps [pyflakes](https://github.com/PyCQA/pyflakes) from 2.1.1 to 2.2.0.
- [Release notes](https://github.com/PyCQA/pyflakes/releases)
- [Changelog](https://github.com/PyCQA/pyflakes/blob/master/NEWS.rst)
- [Commits](https://github.com/PyCQA/pyflakes/commits)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]

requirements.txt

@@ -3,6 +3,6 @@ flake8==3.7.9
 mccabe==0.6.1
 mypy==0.770
 pycodestyle==2.5.0
-pyflakes==2.1.1
+pyflakes==2.2.0
 typed-ast==1.4.1
 wheel==0.34.2