* test/lib/test/unit/assertions.rb (assert_raise_with_message):
  set default internal encoding to the excpected message, which
  affects String#inspect in messages.

* test/lib/test/unit/assertions.rb (assert_warning): ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54522 b2dd03c8-39d4-4d8f-98ff-823fe69b080e