formatting: using black to check for formatting

formatting: run black version 19.10b0 on the codebase The latest version of black is out and contains the change we needed. So we can start using it now. note: `test-check-format.t` will complains about this changes because it still use `grey` and need to be migrated to `black`. See next changesets for this.

packaging: fix buildrpm whitespace

packaging: drop outdated buildrpm "tested on" comment Packaging usually works on other versions too, and it is not efficient to maintain the list in repo. It is already out of sync with the Makefile targets.