run-tests: add #require to abort full test

This allows nuking a bunch of ugly hghave || exit 80 lines.

--HG--
extra : amend_source : fd0879ce28be6efe9e6e8d2134a20c924d4036cd
tests: replace exit 80 with #require

--HG--
extra : rebase_source : fdcc9c7d1a97a1c367785409d76ce0af9dca86c9
tests: change some #ifs to #requires