assertions.rb: refine message

* test/lib/test/unit/assertions.rb (assert_raise_with_message):
  refine default message for the exception to be raised.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46568 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/lib/test/unit/assertions.rb

@@ -126,7 +126,7 @@ module Test
           raise TypeError, "Expected #{expected.inspect} to be a kind of String or Regexp, not #{expected.class}"
         end
 
-        ex = assert_raise(exception, *msg) {yield}
+        ex = assert_raise(exception, msg || proc {"Exception(#{exception}) with message matches to #{expected.inspect}"}) {yield}
         msg = message(msg, "") {"Expected Exception(#{exception}) was raised, but the message doesn't match"}
 
         if assert == :assert_equal