Bump isort from 5.8.0 to 5.9.1

Bumps [isort](https://github.com/pycqa/isort) from 5.8.0 to 5.9.1.
- [Release notes](https://github.com/pycqa/isort/releases)
- [Changelog](https://github.com/PyCQA/isort/blob/main/CHANGELOG.md)
- [Commits](PyCQA/isort@5.8.0...5.9.1)

---
updated-dependencies:
- dependency-name: isort
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

requirements_test.txt

@@ -2,7 +2,7 @@ aresponses==2.1.4
 coverage==5.4
 flake8==3.9.2
 flake8-docstrings==1.6.0
-isort==5.8.0
+isort==5.9.1
 mypy==0.800
 pylint==2.9.3
 pytest==6.2.3