* test/rubygems/test_gem_commands_setup_command.rb: @ui uses StringIO
  as its streams, and Encoding.default_external does not effect to
  stringIOs already exist.  so, we need to set external_encoding of
  @ui.outs directly.  this problem (test failure) does not appear in
  the environments default_external is us-ascii or utf-8.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47624 b2dd03c8-39d4-4d8f-98ff-823fe69b080e