test_module.rb: fix encoding

* test/ruby/test_module.rb (test_const_set_invalid_name): warning
  message encoding depends on Encoding.default_internal.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48475 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_module.rb

@@ -686,7 +686,9 @@ class TestModule < Test::Unit::TestCase
     assert_raise(NameError) { c1.const_set("X\u{3042}".encode("utf-32be"), :foo) }
     assert_raise(NameError) { c1.const_set("X\u{3042}".encode("utf-32le"), :foo) }
     cx = EnvUtil.labeled_class("X\u{3042}")
-    assert_raise_with_message(TypeError, /X\u{3042}/) { c1.const_set(cx, :foo) }
+    EnvUtil.with_default_internal(Encoding::UTF_8) {
+      assert_raise_with_message(TypeError, /X\u{3042}/) { c1.const_set(cx, :foo) }
+    }
   end
 
   def test_const_get_invalid_name