suppress warnings: URI.regexp is obsolete

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46572 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Revert r46568 "assertions.rb: refine message"

Don't inspect exceptions without backtrace omission for SystemStackError.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46573 b2dd03c8-39d4-4d8f-98ff-823fe69b080e