Part of #9744
Removes all redundant `# -*- coding: utf-8 -*-` lines from files, as python 3 automatically reads source code as utf-8 now.
`Signed-off-by: Jonathan de Jong <jonathan@automatia.nl>`
- Update black version to the latest
- Run black auto formatting over the codebase
- Run autoformatting according to [`docs/code_style.md
`](80d6dc9783/docs/code_style.md)
- Update `code_style.md` docs around installing black to use the correct version
prometheus_client 0.5 has a named-tuple Sample type with more member
than the old plain tuple had. This commit makes sure the unit test
detects this and changes the way it reads the sample.
Signed-off-by: Maarten de Vries <maarten@de-vri.es>
