test_regex_casefold.rb: skip if no data file

* test/ruby/enc/test_regex_casefold.rb (setup): skip with error
  message if CaseFolding.txt does not present, instead of printing
  the message, which causes unknown command in parallel test.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56017 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/enc/test_regex_casefold.rb

@@ -37,7 +37,7 @@ class TestCaseFold < Test::Unit::TestCase
     @@tests ||= read_tests
   rescue Errno::ENOENT => e
     @@tests ||= []
-    puts e.message
+    skip e.message
   end
 
   def self.generate_test_casefold(encoding)