PR11772 backport https://github.com/bitcoin/bitcoin/pull/11772/files
e97b113b04 [tests] Change invalidblockrequest to use BitcoinTestFramework (John Newbery)
2b7064eda7 [tests] Fix flake8 warnings in invalidblockrequest (John Newbery)
54b8c580b7 [test] Fix nits leftover from 11771 (Conor Scott)
Pull request description:
Builds on #11771. Please review that PR first Next step in #10603. - first commit tidies up invalidblockrequest.py - second commit removes usage of ComparisonTestFramework