Bump xenon from 0.8.0 to 0.9.1

Bumps [xenon](https://github.com/rubik/xenon) from 0.8.0 to 0.9.1.
- [Changelog](https://github.com/rubik/xenon/blob/master/CHANGELOG)
- [Commits](rubik/xenon@v0.8.0...v0.9.1)

---
updated-dependencies:
- dependency-name: xenon
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

setup.py

@@ -8,7 +8,7 @@
     "asynctest==0.13.0",
     "pytz",
     "pylint==2.11.1",
-    "xenon==0.8.0",
+    "xenon==0.9.1",
     "black==20.8b1",
     "isort==5.10.1",
     "async_generator==1.10;python_version=='3.6.*'",