add message for an assertion.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@10380 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ripper/test_files.rb

@@ -13,7 +13,7 @@ class TestRipper_Generic < Test::Unit::TestCase
   def test_parse_files
     Find.find("#{SRCDIR}/lib", "#{SRCDIR}/ext", "#{SRCDIR}/sample", "#{SRCDIR}/test") {|n|
       next if /\.rb\z/ !~ n || !File.file?(n)
-      assert_nothing_raised { Parser.new(File.read(n)).parse }
+      assert_nothing_raised("ripper failed to parse: #{n.inspect}") { Parser.new(File.read(n)).parse }
     }
   end
 end